不知道它是否正是您要查找的内容，但此短片段将自定义类添加到nav菜单项：

add_filter(\'nav_menu_css_class\' , \'wpse_143574_nav_class\' , 10 , 2);
function wpse_143574_nav_class($classes, $item){

         $classes[] = "my-class";

     }
     return $classes;
}

EDIT: $item 通常很有用，例如if ( $item->title == \'Contact\')

您可以这样做：

// where "Top" is menu name, slug or id. But not menu location.
$menu_items = wp_get_nav_menu_items( \'Top\' );

foreach ( $menu_items as $menu_item ) {
  $menu_classes = $menu_item->classes;

  foreach ( $menu_classes as $menu_class ) {
    if ( \'mycustomclass\' === $menu_class ) {
        return true;
    }
  }
}