protected function sendVideoMsgToJsonString(WxSendVideoMsg $msg)
    {
        $formatStr = '{
                        "touser":"%s",
                        "msgtype":"%s",
                        "video":
                        {
                          "media_id":"%s",
                          "thumb_media_id":"%s",
                          "title":"%s",
                          "description":"%s"
                        }
                    }';
        $result = sprintf($formatStr,   $msg->getToUserName(),
                                        $msg->getMsgType(),
                                        $msg->getMediaId(),
                                        $msg->getThumbMediaId(),
                                        $msg->getTitle(),
                                        $msg->getDescription()
                        );

        return $result;
    }