Adding Class To The WordPress Page Menu

Problem: You need to add a class or id to the the unordered list in wp_page_menu. Maybe to implement some super-slick drop down page menus. But! That <ul> tag is trapped inside of wp_page_menu. What are you going to do?

Solution: Filter wp_page_menu. In the code example below we’ll use preg_replace to find the first—and only the first—

<ul> tag and swap it out for <ul id="nav">. Just drop this code snippet into your theme’s functions.php file and you’re set.
// Add ID and CLASS attributes to the first <ul> occurence in wp_page_menu


function add_menuclass($ulclass) {
return preg_replace('/<ul>/', '<ul id="nav">', $ulclass, 1);
}
add_filter('wp_page_menu','add_menuclass');