有时候，我们会遇到子分类特别多，而且还要添加到网站导航中的情况。如果导航中只有分类还好弄，可是还有其他自定义菜单项的话，就比较麻烦了。多数时候，要手动去添加顶级分类下的子分类，很费时。下面说下，如何在菜单本身是分类的情况下，自动添加其下的子分类为子菜单。

代码

/* 自动给导航菜单中的分类添加其下的子分类 */
add_filter("wp_get_nav_menu_items", function($items, $menu, $args) {
    if (is_admin()) {
        return $items;
    }

    foreach ($items as $index => $i) {
        if ("category" !== $i->object) {
            continue;
        }
        $term_children = get_term_children($i->object_id, "category");
        foreach ($term_children as $index2 => $child_id) {
            $child               = get_term($child_id);
            $url                 = get_term_link($child);
            $e                   = new stdClass();
            $e->title            = $child->name;
            $e->url              = $url;
            $e->menu_order       = 500 * ($index + 1) + $index2;
            $e->post_type        = "nav_menu_item";
            $e->post_status      = "published";
            $e->post_parent      = $i->ID;
            $e->menu_item_parent = $i->ID;
            $e->type             = "custom";
            $e->object           = "custom";
            $e->ID               = 0;
            $e->db_id            = 0;
            $e->object_id        = 0;
            $e->classes          = array();
            $e->description      = "";
            $items[]             = $e;
        }
    }
    return $items;
}, 10, 3);