protected function sendNewsMsgToJsonString(WxSendNewsMsg $msg)
    {
        $itemArray  = $msg->getAllArticleItems();
        $itemStr    = '';
        foreach ($itemArray as $item) {
            $itemStr .= $this->sendNewsItemToJsonString($item) . ',';
        }

        $itemStr    = substr($itemStr, 0, -1);

        $formatStr = '{
                        "touser":"%s",
                        "msgtype":"%s",
                        "news":{
                            "articles": [
                             %s
                             ]
                        }
                    }';

        $result = sprintf($formatStr,   $msg->getToUserName(),
                                        $msg->getMsgType(),
                                        $itemStr
                            );

        return $result;
    }