我想在侧边栏菜单中使用“depth”只显示第一个子页面，我想知道我应该在代码中的什么地方插入depth？我想只显示第一个子页面，而不是所有子页面。我已尝试在此if条件下插入“depth”

if ( $item->current_item_ancestor && $item->menu_item_parent == \'0\' )
{
    $last_parent = $item,
    \'depth\' => 1
}

/* ------------------------------------------------------------------- */

function myproject_nav_menu_objects_start_in( $sorted_menu_items, $args )
{

   switch ( $args->menu_id )
   {
       case \'sidebar-menu\' :

       $current = false;
       $last_parent = false;
       $menu = array();

       foreach( $sorted_menu_items as $item )
       {
           if ( $item->current_item_ancestor && $item->menu_item_parent == \'0\' )
               $last_parent = $item;

           if ( $item->current )
               $current = $item;
       }

       if ( $current ) 
       {
           $keys = array();
           $last_parent = ( ! $last_parent ) ? $current : $last_parent;

           $children = _myproject_submenu_get_children_ids( $last_parent->ID, $sorted_menu_items );

           foreach ( $sorted_menu_items as $key => $item ) 
           {
               if ( ! in_array( $item->ID, $children ) )
                   unset( $sorted_menu_items[$key] );
           }

       }
       else
       {
           $sorted_menu_items = array();
       }

       break;

   }
   return $sorted_menu_items;
}
add_filter( \'wp_nav_menu_objects\', \'myproject_nav_menu_objects_start_in\', 10, 2 );