After updating to 1.5.5b,i got the following debug file for my payment method.

The php code for firstonecc.php from line 312 is
PHP Code:
        $xml = new DOMDocument();
        $xml->loadXML($result);
        $amount = $xml->getElementsByTagName('amount')->item(0)->nodeValue;
        $bankInfo = $xml->getElementsByTagName('bankInfo')->item(0)->nodeValue;
        $currency = $xml->getElementsByTagName('currency')->item(0)->nodeValue;
        $errorCode = $xml->getElementsByTagName('errorCode')->item(0)->nodeValue;
        $errorMsg = $xml->getElementsByTagName('errorMsg')->item(0)->nodeValue;
        $md5Info = $xml->getElementsByTagName('md5Info')->item(0)->nodeValue;
        $orderNo = $xml->getElementsByTagName('orderNo')->item(0)->nodeValue;
        $succeed = $xml->getElementsByTagName('succeed')->item(0)->nodeValue;
        $tradeNo = $xml->getElementsByTagName('tradeNo')->item(0)->nodeValue;
        //$validateUrl = $xml->getElementsByTagName('validateUrl')->item(0)->nodeValue;
        $merKey = trim(MODULE_PAYMENT_FRISTONECC_MD5KEY);
        $md5src = $tradeNo . $orderNo . $merKey . $succeed . $currency . $amount;
        $resultMsg=$bankInfo ? $bankInfo : $errorMsg;
        //MD5检验结果
        $md5sign = strtoupper(md5($md5src));
        if ($md5sign == $md5Info) {
            if ($succeed == 0) {
                
                $db->Execute("insert into " . TABLE_ORDERS_STATUS_HISTORY . " (comments, orders_id, orders_status_id, date_added, customer_notified) values ('TradeNo:" . zen_db_input($tradeNo . "  ||BillNo:" . $orderNo . "  ||Amount:" . $amount . $currency . " ||errorMsg:" . $resultMsg) . " ' , '" . $insert_id . "', '519', now(), '1')");
                $db->Execute("update " . TABLE_ORDERS . " SET orders_status = 519 Where orders_id = '" . $insert_id . "'");
                $this->send_email();

                $messageStack->add_session('checkout_payment', 'Sorry,Payment Failure,The reason is : '. $resultMsg . ' Please pay again !', 'error');
            
                 zen_redirect(zen_href_link(FILENAME_CHECKOUT_PAYMENT, '', 'SSL', true, false)); 

The debug file i got as following

[01-Dec-2016 02:57:34 UTC] Request URI: /index.php?main_page=checkout_confirmation, IP address: 14.177.143.115
#1 DOMDocument->loadXML() called at [/home/estanda1/public_html/includes/modules/payment/Fristonecc.php:313]
#2 Fristonecc->pre_confirmation_check() called at [/home/estanda1/public_html/includes/classes/payment.php:213]
#3 payment->pre_confirmation_check() called at [/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php:95]
#4 require(/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php) called at [/home/estanda1/public_html/index.php:36]

[01-Dec-2016 02:57:34 UTC] PHP Warning: DOMDocument::loadXML(): Opening and ending tag mismatch: meta line 9 and head in Entity, line: 25 in /home/estanda1/public_html/includes/modules/payment/Fristonecc.php on line 313
[01-Dec-2016 02:57:34 UTC] Request URI: /index.php?main_page=checkout_confirmation, IP address: 14.177.143.115
#1 DOMDocument->loadXML() called at [/home/estanda1/public_html/includes/modules/payment/Fristonecc.php:313]
#2 Fristonecc->pre_confirmation_check() called at [/home/estanda1/public_html/includes/classes/payment.php:213]
#3 payment->pre_confirmation_check() called at [/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php:95]
#4 require(/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php) called at [/home/estanda1/public_html/index.php:36]

[01-Dec-2016 02:57:34 UTC] PHP Warning: DOMDocument::loadXML(): Entity 'bull' not defined in Entity, line: 36 in /home/estanda1/public_html/includes/modules/payment/Fristonecc.php on line 313
[01-Dec-2016 02:57:34 UTC] Request URI: /index.php?main_page=checkout_confirmation, IP address: 14.177.143.115
#1 DOMDocument->loadXML() called at [/home/estanda1/public_html/includes/modules/payment/Fristonecc.php:313]
#2 Fristonecc->pre_confirmation_check() called at [/home/estanda1/public_html/includes/classes/payment.php:213]
#3 payment->pre_confirmation_check() called at [/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php:95]
#4 require(/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php) called at [/home/estanda1/public_html/index.php:36]

[01-Dec-2016 02:57:34 UTC] PHP Warning: DOMDocument::loadXML(): Entity 'bull' not defined in Entity, line: 100 in /home/estanda1/public_html/includes/modules/payment/Fristonecc.php on line 313
[01-Dec-2016 02:57:34 UTC] Request URI: /index.php?main_page=checkout_confirmation, IP address: 14.177.143.115
#1 DOMDocument->loadXML() called at [/home/estanda1/public_html/includes/modules/payment/Fristonecc.php:313]
#2 Fristonecc->pre_confirmation_check() called at [/home/estanda1/public_html/includes/classes/payment.php:213]
#3 payment->pre_confirmation_check() called at [/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php:95]
#4 require(/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php) called at [/home/estanda1/public_html/index.php:36]

[01-Dec-2016 02:57:34 UTC] PHP Warning: DOMDocument::loadXML(): Entity 'bull' not defined in Entity, line: 102 in /home/estanda1/public_html/includes/modules/payment/Fristonecc.php on line 313
[01-Dec-2016 02:57:34 UTC] Request URI: /index.php?main_page=checkout_confirmation, IP address: 14.177.143.115
#1 DOMDocument->loadXML() called at [/home/estanda1/public_html/includes/modules/payment/Fristonecc.php:313]
#2 Fristonecc->pre_confirmation_check() called at [/home/estanda1/public_html/includes/classes/payment.php:213]
#3 payment->pre_confirmation_check() called at [/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php:95]
#4 require(/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php) called at [/home/estanda1/public_html/index.php:36]

[01-Dec-2016 02:57:34 UTC] PHP Warning: DOMDocument::loadXML(): Premature end of data in tag body line 26 in Entity, line: 111 in /home/estanda1/public_html/includes/modules/payment/Fristonecc.php on line 313
[01-Dec-2016 02:57:34 UTC] Request URI: /index.php?main_page=checkout_confirmation, IP address: 14.177.143.115
#1 DOMDocument->loadXML() called at [/home/estanda1/public_html/includes/modules/payment/Fristonecc.php:313]
#2 Fristonecc->pre_confirmation_check() called at [/home/estanda1/public_html/includes/classes/payment.php:213]
#3 payment->pre_confirmation_check() called at [/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php:95]
#4 require(/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php) called at [/home/estanda1/public_html/index.php:36]

[01-Dec-2016 02:57:34 UTC] PHP Warning: DOMDocument::loadXML(): Premature end of data in tag head line 6 in Entity, line: 111 in /home/estanda1/public_html/includes/modules/payment/Fristonecc.php on line 313
[01-Dec-2016 02:57:34 UTC] Request URI: /index.php?main_page=checkout_confirmation, IP address: 14.177.143.115
#1 DOMDocument->loadXML() called at [/home/estanda1/public_html/includes/modules/payment/Fristonecc.php:313]
#2 Fristonecc->pre_confirmation_check() called at [/home/estanda1/public_html/includes/classes/payment.php:213]
#3 payment->pre_confirmation_check() called at [/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php:95]
#4 require(/home/estanda1/public_html/includes/modules/pages/checkout_confirmation/header_php.php) called at [/home/estanda1/public_html/index.php:36]

[01-Dec-2016 02:57:34 UTC] PHP Warning: DOMDocument::loadXML(): Premature end of data in tag html line 5 in Entity, line: 111 in /home/estanda1/public_html/includes/modules/payment/Fristonecc.php on line 313