Programmatically (PHP) get the nr. of items in the primary navigation menu

Question

I need to get the nr. of items in the primary navigation menu. I need this to determine the width in percentage of each list item. So I also need to change/add to the css width attribute of the list items somehow, which I haven't figured out how to do yet either... As a first attempt I've tried the function wp_get_nav_menu_object. I am developing a child theme off of the twentyfifteen template. I have made a custom home page where I load the primary navigation (copied straight from the sidebar.php file in the original theme folder) and call wp_get_nav_menu_object straight after that using the code snippet

<?php if (has_nav_menu('primary')) : ?>   
   <nav id="site-navigation" class="main-navigation" role="navigation">
      <?php
       // Primary navigation Menu
       wp_nav_menu(array(
         'menu_class' => 'nav-menu',
         'theme_location' => 'primary',
       ));
       // none of these seem to work...
       //$menu = wp_get_nav_menu_object('menu-primary-menu');
       $menu = wp_get_nav_menu_object('primary');
       echo $menu->count;
     ?>   
   </nav> <!-- /.main-navigation --> 
<?php endif; ?>

I know I could go with a jQuery/JavaScript solution (which is what I'm doing at the moment in fact), but that's not ideal. I'm beginning to suspect that for what I want to do I need to create my own custom primary navigation menu with the help of the Walker class. Could anybody advise me on what the best approach would be?

Answer 1

You are not providing the correct parameter to wp_get_nav_menu_object() function. It needs the menu ID or menu slug but you are providing the menu theme location. Obviously, I can not tell you what is the ID or slug of your menu.

One way of getting the menu ID of the menu assigned to theme location is using get_nav_menu_locations():

$menu = wp_get_nav_menu_object( get_nav_menu_locations()['primary'] );
echo $menu->count;