eventCode; $flag = $ctuRequest->flag; $data = $ctuRequest->data; ksort($data); $paramStr = self::$EVENT_CODE . $eventCode . self::$FLAG . $flag; foreach ($data as $key => $value) { if (is_null($value)) { $paramStr .= $key . "null"; } else { $paramStr .= $key . $value; } } return $paramStr; } }