How-to inspect filter-able $vars?
Example Nav menu walker – allows adding eg. css classes to (all) menu items. // copyied from /wp-core/wp-includes/nav-menu-template.php > line 76 (wp 3.1.1) – start_el() function $class_names = join( ‘ ‘, apply_filters( ‘nav_menu_css_class’, array_filter( $classes ), $item, $args ) ); Now let’s check the $var: function wpse15319_check_nav_menu_classes( $classes ) { // You can take any … Read more