/**
  * @param string      $msg
  * @param SamlMessage $message
  * @param string|null $destination
  *
  * @return string
  */
 protected function getDestinationUrl($msg, SamlMessage $message, $destination)
 {
     $destination = $message->getDestination() ? $message->getDestination() : $destination;
     if (strpos($destination, '?') === false) {
         $destination .= '?' . $msg;
     } else {
         $destination .= '&' . $msg;
     }
     return $destination;
 }