Display Search Box Secondary Nav Menu WordPress

function add_search_box_secondary_menu($items, $args) { 
if ($args->theme_location == 'secondary') {
        ob_start(); 
        get_search_form(); 
        $searchform = ob_get_contents(); 
        ob_end_clean(); 
  
    $items .= '<li class="searchbox">' . $searchform . '</li>'; 
  }
  return $items;    
       
}
/**
* @author Brad Dalton - WP Sites
* @link http://wpsites.net/
*/
add_filter('wp_nav_menu_items','add_search_box_secondary_menu', 10, 2);