WordPress中文手册

很多网页设计都会给菜单之间加一个分割线，最常见的就是“|”了，如图：

我们需要的是，每个菜单项之间有一个分隔符。传统的方法是配置WordPress的菜单输出函数wp_nav_menu，给它加上一个after参数，

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.PHP文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_CSS_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

这样可以给每个菜单项的后面加一个字符，且html结构如下

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

这样有个显而易见的缺点就是每个菜单项后面都有个竖线，最后一个菜单项也有，可是我们肯定不需要菜单的最后面也出现竖线，当然这样的结构，通过css还是可以写出上面图片中的样式的。

我们要的效果：以及菜单每个菜单项后面加一个分割线，菜单的最后面不要，二级菜单不要。

分析：wp_nav_menu函数输出菜单项的代码在 wp-includes/nav-menu-template.php文件里面，具体的呢，在文件中Walker_Nav_Menu类里面的start_el函数，所以，方法就是改造这个函数。

步骤一：找到wp_nav_menu函数，增加一个walker参数，如下：

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

关于walker参数的用法，请参考官网。

步骤二：前面的代码中walker参数的值，后面是一个类，类名是ashuwp_navwolker，所以第二部就是新建这个类，如下：

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

新定义一个ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu，然后将Walker_Nav_Menu类的start_el函数直接复制进去，复制完后，如下：

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

步骤三：改造ashuwp_navwalker类中的start_el函数。

1.在start_el函数开头，定义一个静态数组变量，用来计数，用数组可以支持多个菜单。注意数组中的初始值，需要支持多少个菜单，都需要手动加上，静态变量用来记每个输出的菜单里面的一级菜单的数量。

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

2.添加计算菜单中一级菜单数量的函数。该函数不需要放入类中，随便放在主题的functions.php文件的某一位置。

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

3.重新定义$args-after的值，将下面的代码加入start_el函数中。

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

做好1 3两个点之后， ashuwp_navwalker extends类如下：

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

至此，就可以完成了。

懒人专用

将下列代码复制到你的主题的functions.php文件中

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>  

然后修改你的wp_nav_menu函数，添加walker参数

<?php   
$args = array(   
    'after'=>'|' //菜单项后面加|字符   
);   
wp_nav_menu($args);   
?>  


<ul>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
    <li><a href="">阿树工作室</a>|</li>   
</ul>  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   //注意这个theme-location参数
);   
wp_nav_menu($args);   
?>  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
  
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
        //......  


//参数$menu_id为菜单id   
function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}  


/***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  


//定义ashuwp_navwalker类，继承wp-includes/nav-menu-template.php文件中的Walker_Nav_Menu   
class ashuwp_navwalker extends Walker_Nav_Menu {   
    //在中间添加函数，直接复制Walker_Nav_Menu类的start_el函数进来   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //定义静态变量$top_level_count 数组中的值对应多个wp_nav_menu函数中的theme_location参数的值   
        static $top_level_count = array('ashuwp-menu'=>0,'ashuwp-nav'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes =empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


function ashuwp_count_top_level_menu_items($menu_id){   
    $count = 0;   
    $menu_items = wp_get_nav_menu_items($menu_id);   
    foreach($menu_items as $menu_item){   
        if($menu_item->menu_item_parent==0){   
            $count++;   
        }   
    }   
    return $count;   
}   
  
class ashuwp_navwalker extends Walker_Nav_Menu {   
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {   
        //根据实际增加和修改下面的数组   
        static $top_level_count = array('ashu-menu'=>0,'top-menu'=>0);   
           
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';   
  
        $class_names = $value = '';   
  
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;   
        $classes[] = 'menu-item-' . $item->ID;   
  
        /** 
         * Filter the CSS class(es) applied to a menu item's <li>.  
         *  
         * @since 3.0.0  
         *  
         * @param array  $classes The CSS classes that are applied to the menu item's <li>.  
         * @param object $item    The current menu item.  
         * @param array  $args    An array of arguments. @see wp_nav_menu()  
         */  
        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );   
        $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';   
  
        /** 
         * Filter the ID applied to a menu item's <li>.  
         *  
         * @since 3.0.1  
         *  
         * @param string The ID that is applied to the menu item's <li>.  
         * @param object $item The current menu item.  
         * @param array $args An array of arguments. @see wp_nav_menu()  
         */  
        $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );   
        $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';   
  
        $output .= $indent . '<li' . $id . $value . $class_names .'>';   
  
        $atts = array();   
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';   
        $atts['target'] = ! empty( $item->target )     ? $item->target     : '';   
        $atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';   
        $atts['href']   = ! empty( $item->url )        ? $item->url        : '';   
  
        /** 
         * Filter the HTML attributes applied to a menu item's <a>.  
         *  
         * @since 3.6.0  
         *  
         * @param array $atts {  
         *     The HTML attributes applied to the menu item's <a>, empty strings are ignored.  
         *  
         *     @type string $title  The title attribute.  
         *     @type string $target The target attribute.  
         *     @type string $rel    The rel attribute.  
         *     @type string $href   The href attribute.  
         * }  
         * @param object $item The current menu item.  
         * @param array  $args An array of arguments. @see wp_nav_menu()  
         */  
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );   
  
        $attributes = '';   
        foreach ( $atts as $attr => $value ) {   
            if ( ! empty( $value ) ) {   
                $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );   
                $attributes .= ' ' . $attr . '="' . $value . '"';   
            }   
        }   
           
        /***add code****/  
        $args->after='';   
        if($item->menu_item_parent==0 and $top_level_count[$args->theme_location]!==null){ //Count top level menu items   
            $top_level_count[$args->theme_location]++; //Increment   
        }   
        $location_name = $args->theme_location;   
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $location_name ] ) ) {   
            $main_nav = wp_get_nav_menu_object( $locations[ $location_name ] );   
            if($item->menu_item_parent==0  && $top_level_count[$args->theme_location]!=ashuwp_count_top_level_menu_items($main_nav->term_id)){   
                $args->after= '<span class="menu_line">|</span>';   
            }   
        }   
        /*****add code*****/  
           
        $item_output = $args->before;   
        $item_output .= '<a'. $attributes .'>';   
        /** This filter is documented in wp-includes/post-template.php */  
        $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;   
        $item_output .= '</a>';   
        $item_output .= $args->after;   
  
        /** 
         * Filter a menu item's starting output.  
         *  
         * The menu item's starting output only includes $args->before, the opening <a>,  
         * the menu item's title, the closing </a>, and $args->after. Currently, there is  
         * no filter for modifying the opening and closing <li> for a menu item.  
         *  
         * @since 3.0.0  
         *  
         * @param string $item_output The menu item's starting HTML output.  
         * @param object $item        Menu item data object.  
         * @param int    $depth       Depth of menu item. Used for padding.  
         * @param array  $args        An array of arguments. @see wp_nav_menu()  
         */  
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );   
    }   
}  


<?php   
$args = array(   
    'depth'=>2, //支持二级菜单   
    'walker' => new ashuwp_navwalker(), //后面的ashuwp_navwolker是类名   
    'theme_location' => 'ashuwp-menu'   
);   
wp_nav_menu($args);   
?>