add_filter(\'nav_menu_css_class\' , \'special_nav_class\' , 10 , 2);
function special_nav_class ($classes, $item) {
if (in_array(\'current-post-ancestor\', $classes) || in_array(\'current-page-ancestor\', $classes) || in_array(\'current-menu-item\', $classes) ){
$classes[] = \'active \';
}
return $classes;
}