'menu_item_parent', 'id' => 'db_id', ); * * Starts the list before the elements are added. * * @since 3.0.0 * * @see Walker::start_lvl() * * @param string $output Used to append additional content (passed by reference). * @param int $depth Depth of menu item. Used for padding. * @param stdClass $args An object of wp_nav_menu() arguments. public function start_lvl( &$output, $depth = 0, $args = null ) { if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) { $t = ''; $n = ''; } else { $t = "\t"; $n = "\n"; } $indent = str_repeat( $t, $depth ); Default class. $classes = array( 'sub-menu' ); * * Filters the CSS class(es) applied to a menu list element. * * @since 4.8.0 * * @param string[] $classes Array of the CSS classes that are applied to the menu `