給Wordpress的次選單之parent加上class，將擁有submenu的li，添加一個指定的class進去

add_class_to_a_parent_of_a_submenu.php

<?php
/*
 * This adds a "dropdown" class to menus
 */
function oikos_add_menu_parent_classes( $classes, $item, $args ) {
  $children = get_posts( array(
                               'meta_query' => array (
                                                  array(
                                                     'key' => '_menu_item_menu_item_parent',
                                                     'value' => $item->ID )
                                                       ),
                               'post_type' => $item->post_type ) );
  if (count($children) > 0) {
    array_push($classes,'dropdown'); // add the class .dropdown to the current menu item
  }
  return $classes;
}
add_filter( 'nav_menu_css_class', 'oikos_add_menu_parent_classes', 10, 3 );