Paypal沙箱 - 错误：此付款尝试已处理完毕？是什么导致这个？

Question

过去几个月我一直在使用Sandbox测试我的网站，直到昨天一切都很顺利。现在，当我尝试付款时，我得到了上述错误。我甚至设置了额外的假用户帐户，但我得到了相同的结果。我没有触及IPN监听器PHP文件，所以我被卡住了。任何人都可以了解可能的原因吗？另一个奇怪的事情 - 监听器确实接收数据并正确更新数据库，但Paypal显示错误。

这是监听器文件（但请记住，我已经很长时间没有触及它了）：

    include_once 'functions.php';

    $paypal = new PAYPAL_IPN('sandbox');        // change to 'live' for real paypal
    $paypal->run();

    class Paypal_IPN
    {   
        /** @var string $_url The paypal url to go to through cURL*/
        private $_url;
        /**
        * @param string $mode 'live' or 'sandbox'
        */
        public function __construct($mode = 'live')
        {
            if ($mode == 'live')


$this->_url = 'https://www.paypal.com/cgi-bin/webscr';

        else
        $this->_url = 'https://www.sandbox.paypal.com/cgi-bin/webscr';
    }

    public function run()
    {
      $postFields = 'cmd=_notify-validate';
        $product_price1 = 7.50;      
        $product_price2 = 13.50;    
        $product_price3 = 19.00;    
        $currency_code = 'USD';     

        foreach($_POST as $key => $value)
        {
            $postFields .= "&$key=".urlencode($value);
        }

        $ch = curl_init();

        curl_setopt_array($ch, array(
            CURLOPT_URL => $this->_url,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_SSL_VERIFYPEER => false,
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => $postFields
        ));

        $result = curl_exec($ch);
        curl_close($ch);

        $fh = fopen('result.txt', 'w');
        fwrite($fh, $result .' ... '. $postFields);
        fclose($fh);        

    if (strcmp ($result, "VERIFIED") == 0) {        // PAYMENT VALID 

        $errors = array();                                         
                                                    // Check payment status
        if ($_POST['payment_status'] != 'Completed') {
            $errors[] .= "Payment not completed";
        }
                                                    // Check seller e-mail
        if ($_POST['receiver_email'] != 'salesfmp@fixmypixels.net')  {
            $errors[] .= "Incorrect seller e-mail";
        }

                                       // Check the currency code
       if ($_POST['mc_currency'] != $currency_code)  {
            $errors[] .= "Incorrect currency code";
        }
                                       // Check transaction id
      $txn_id = ($_POST['txn_id']);

      $sql = "SELECT COUNT(*) AS count FROM repairs WHERE txn_id = '$txn_id'";
        $q = mysql_query($sql);
      $f = mysql_fetch_array($q);

        } // end of if (strcmp ($result, "VERIFIED") == 0)

        if($f['count'] > 0) {
            $errors[] .= "Transaction already processed";
            } 
        else 
            {           
            if (count($errors) > 0) {
                // IPN data is incorrect - possible fraud
                // It is a good practice to send the transaction details to your e-mail and investigate manually
                // Email Headers

                $headers = "From: salesfmp@email.net \r\n";
                $headers .= "Reply-To: . salesfmp@email.net \r\n";
                $headers .= "MIME-Version: 1.0\r\n";
                $headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";
                $message = "Transaction number = ".$txn_id."   .....    IPN failed fraud checks " . print_r( $errors, true );

                mail('joe@email.net', 'IPN Fraud Warning', $message, $headers);
                } 
            else {                                  // PayPal payment is valid and NO other errors      

            $verified = 1;                          // IPN transaction data is valid 1 = Verified, 0 = Invalid

                $last_name = sanitizeString($_POST['last_name']);       // buyer's last name
                $first_name = sanitizeString($_POST['first_name']);     // buyer's first name
                $file_name = sanitizeString($_POST['file_name']);       // submitted photo's file name 
                $payer_email = sanitizeString($_POST['payer_email']);   // buyer's email address
                $txn_type = sanitizeString($_POST['txn_type']);         // should be  = "web_accept"
                $txn_id = sanitizeString($_POST['txn_id']);             // transaction ID number - unique # from Paypal
                $payment_date = sanitizeString($_POST['payment_date']); // Paypal's date of transaction

                $payment_amount = sanitizeString($_POST['mc_gross']);

            $_SESSION['payment_amount'] = $payment_amount;          // used in paypal_success.php

            if($payment_amount == $product_price1) {
               $quantity = 1;                                           // quantity purchased =  1
            } elseif($payment_amount == $product_price2) {
               $quantity = 2;
            } elseif($payment_amount == $product_price3) {
               $quantity = 3;
            }

            $payment_currency = sanitizeString($_POST['mc_currency']);
                $addr_street = sanitizeString($_POST['address_street']);
                $addr_city = sanitizeString($_POST['address_city']);
                $addr_state = sanitizeString($_POST['address_state']);
                $addr_zip = sanitizeString($_POST['address_zip']);
                $addr_country_code = sanitizeString($_POST['address_country_code']);

                $query = "INSERT INTO repairs (verified, last_name, first_name, file_name, payer_email, txn_type, txn_id, payment_date, qty, mc_gross, mc_currency, address_street, address_city, address_state, address_zip, address_country_code) VALUES ('$verified','$last_name', '$first_name', '$file_name', '$payer_email', '$txn_type', '$txn_id', '$payment_date', '$quantity', '$payment_amount', '$payment_currency', '$addr_street', '$addr_city', '$addr_state', '$addr_zip', '$addr_country_code')";

                $res = mysql_query($query) or die();    

            }   // end else () of if(count($errors) > 0) 

        }   // end of else if($f['count'] > 0)

    }   // end of run()
} // end of Paypal_IPN class
?>