/**
  * Determine which model box type should be rendered
  *
  * @param string $url              URL string.
  * @param string $current_redirect Current redirect by reference.
  *
  * @return string
  */
 private function modal_box_type($url, &$current_redirect)
 {
     if (defined('WPSEO_PREMIUM_FILE') && class_exists('WPSEO_Redirect_Manager')) {
         static $redirect_manager;
         if (!$redirect_manager) {
             $redirect_manager = new WPSEO_Redirect_Manager();
         }
         if ($current_redirect = $redirect_manager->get_redirect($url)) {
             return 'already_exists';
         }
         return 'create';
     }
     return 'no_premium';
 }