_wp_expand_nav_menu_post_data example

$locations      = get_registered_nav_menus();
$menu_locations = get_nav_menu_locations();
$num_locations  = count( array_keys( $locations ) );

// Allowed actions: add, update, delete. $action = isset( $_REQUEST['action'] ) ? $_REQUEST['action'] : 'edit';

/* * If a JSON blob of navigation menu data is found, expand it and inject it * into `$_POST` to avoid PHP `max_input_vars` limitations. See #14134. */
_wp_expand_nav_menu_post_data();

switch ( $action ) {
    case 'add-menu-item':
        check_admin_referer( 'add-menu_item', 'menu-settings-column-nonce' );

        if ( isset( $_REQUEST['nav-menu-locations'] ) ) {
            set_theme_mod( 'nav_menu_locations', array_map( 'absint', $_REQUEST['menu-locations'] ) );
        } elseif ( isset( $_REQUEST['menu-item'] ) ) {
            wp_save_nav_menu_items( $nav_menu_selected_id, $_REQUEST['menu-item'] );
        }