XML 无效标记

我应该怎么做才能防止自定义逍遥游的回调函数中的无效 XML 标记？

$h = fopen("banks/Mybank/log.txt", 'a');
        fwrite($h, 'ConfirmRequest: '.print_r($_REQUEST['ConfirmRequest'],true)."'n");  
        fclose($h);

输出为：

ConfirmRequest: <ConfirmRequest><TransactionId> Cool Attitude  #89</TransactionId><PaymentId>327600020200</PaymentId><PaymentDate>02.10.2013 23:41:26</PaymentDate><Amount>7000</Amount><CardType>VISA!472291******9871</CardType><Status>N</Status><Reason>Declined by merchant</Reason></ConfirmRequest>

结果在

$_REQUEST['ConfirmRequest'];

和

$this->resuest->request['ConfirmRequest'];

====

=========================

非常感谢郁郁的企鹅！ 你能告诉我，我在这里做错了什么吗？

if(
        !openssl_verify(
                       'ConfirmRequest='.$ConfirmRequest,
                        base64_decode($signature),
                        openssl_get_publickey($cert)
                       )
            ) 
            die("signature error");


  $parser = xml_parser_create('');
        xml_parser_set_option($parser, XML_OPTION_TARGET_ENCODING, "UTF-8");
        xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);
            xml_parser_set_option($parser, XML_OPTION_SKIP_WHITE, 1);
        xml_parse_into_struct($parser, $ConfirmRequest, $vals);
        xml_parser_free($parser); 

            foreach ($vals as $data)
                  {
                   if ($data['tag']=='STATUS')
                   $Status=$data['value'];
                   if ($data['tag']=='PAYMENTID')
                   $PaymentId=$data['value'];
                   if ($data['tag']=='PAYMENTDATE')
                   $PaymentDate=$data['value'];
                   if ($data['tag']=='TRANSACTIONID')
                   $TransactionId=$data['value'];
                   if ($data['tag']=='AMOUNT')
                   $Amount=$data['value'];
                   if ($data['tag']=='REASON')
                   $Reason=$data['value'];
               if ($data['tag']=='CARDTYPE')
                   $CardType=$data['value'];
                  }

            $sta = fopen("banks/MyBank/status.txt", 'a');
            fwrite($sta, .print_r($data)."'n"); 
            fclose($sta);   

输出值为"1"...