Limit top level menu items on wp_nav_menu

Question

I've got a situation where I need to limit the top level menu items on a custom menu. The design only has room for 4 fixed width items, and I want to future proof it from displaying more.

Looking at Is there a way to limit the number of top level items in a custom menu?, the answer referred to using wp_nav_menu_items.

Unfortunately, looking through the wordpress.org forums and various blog posts, I can only examples that add items, and nothing that removes them.

When I echo out $items, I only receive a list of each menu item in it's full html. I'm not good enough with regex to figure out how to set a limit to stop after 4 items (and am not sure if that's actually possible with regex anyway).

I have also tried just using css to hide all remaining items through overflow:hidden, but that also hides the dropdowns, so that isn't an option either.

Is there any way I can limit top level items through my custom wp_nav_menu?

Answer 1

A few lines before that filter is this line:

$sorted_menu_items = apply_filters( 'wp_nav_menu_objects', $sorted_menu_items, $args );

That filter passes the top level menu item objects before walk_nav_menu_tree() is called.

Here is some test code:

add_filter( 'wp_nav_menu_objects', 'my_nav_menu_objects', 10, 2 );

function my_nav_menu_objects( $sorted_menu_items, $args ) {
    wp_die( '<pre>' . var_export( $sorted_menu_items, true ) . '</pre>' );
}

It was tested on a 3 item menu. Two top level items and 1 sub menu.

The page tested had only 1 menu on the page. You may have to test the values in $args to find the correct menu on your page.

As expected, $sorted_menu_items returned 3 menu_item objects. The top level menu objects have the 'menu_item_parent' property set to 0.

'menu_item_parent' => '0',

You can use this to find the number of top level menu items.

add_filter( 'wp_nav_menu_objects', 'my_nav_menu_objects', 10, 2 );

function my_nav_menu_objects( $sorted_menu_items, $args ) {

    $top_level_menu_item_ids = array();

    foreach ( $sorted_menu_items as $sorted_menu_item ) {
        if ( 0 == $sorted_menu_item->menu_item_parent )
            $top_level_menu_item_ids[] = $sorted_menu_item->ID;
    }

    wp_die( '<pre>' . var_export( count( $top_level_menu_item_ids ), true ) . '</pre>' );
}

That code should break the page and display the number of top level menu items.

I didn't write the code needed to limit the number of items, but remember that if you remove (unset) a menu item parent, you will also have to remove all of its children.

Here is another test:

function my_nav_menu_objects( $sorted_menu_items, $args ) {

    // Remove a menu item parent, but leave it's child menu item in place.
    unset( $sorted_menu_items[2] );

    return $sorted_menu_items;
}

The result was that the child menu looked like a top level menu on the page.

Answer 2

Based off the response from Charles I was able to complete the code to limit top menu items. It creates a counter of top level menu items and then unsets them after 4. Then, it stores that ID so it can remove any further items that have that item as a parent.

/**
 * Limit number of nav menu items on primary menu
 */
function my_nav_menu_objects( $sorted_menu_items, $args ) {
    if ( $args->theme_location != 'primary' )
        return $sorted_menu_items;
    $unset_top_level_menu_item_ids = array();
    $array_unset_value = 1;
    $count = 1;

    foreach ( $sorted_menu_items as $sorted_menu_item ) {

        // unset top level menu items if over count 4
        if ( 0 == $sorted_menu_item->menu_item_parent ) {
            if ( $count > 4 ) {
                unset( $sorted_menu_items[$array_unset_value] );
                $unset_top_level_menu_item_ids[] = $sorted_menu_item->ID;
            }
            $count++;
        }

        // unset child menu items of unset top level menu items
        if ( in_array( $sorted_menu_item->menu_item_parent, $unset_top_level_menu_item_ids ) )
            unset( $sorted_menu_items[$array_unset_value] );

        $array_unset_value++;
    }

    return $sorted_menu_items;
}
add_filter( 'wp_nav_menu_objects', 'my_nav_menu_objects', 10, 2 );