Paytm支付网关在php中显示错误

I am trying to integrate paytm(merchant/developer account) with Php.I created account in developer paytm and put keys api and secret keys in config file But i am getting error

"Something went wrong It may be due to any of these reasons: Session expired due to inactivity Our system encountered an obstacle".

And page redirect to following url

"https://securegw-stage.paytm.in/theia/{url}"

Here is my TxnTest.php file

<?php
    header("Pragma: no-cache");
    header("Cache-Control: no-cache");
    header("Expires: 0");

?>
    <form method="post" action="pgRedirect.php">
        <table border="1">
            <tbody>
                <tr>
                    <th>S.No</th>
                    <th>Label</th>
                    <th>Value</th>
                </tr>
                <tr>
                    <td>1</td>
                    <td><label>ORDER_ID::*</label></td>
                    <td><input id="ORDER_ID" tabindex="1" maxlength="20" size="20"
                        name="ORDER_ID" autocomplete="off"
                        value="<?php echo  "ORDS" . rand(10000,99999999)?>">
                    </td>
                </tr>
                <tr>
                    <td>2</td>
                    <td><label>CUSTID ::*</label></td>
                    <td><input id="CUST_ID" tabindex="2" maxlength="12" size="12" name="CUST_ID" autocomplete="off" value="CUST001"></td>
                </tr>
                <tr>
                    <td>3</td>
                    <td><label>INDUSTRY_TYPE_ID ::*</label></td>
                    <td><input id="INDUSTRY_TYPE_ID" tabindex="4" maxlength="12" size="12" name="INDUSTRY_TYPE_ID" autocomplete="off" value="Retail"></td>
                </tr>
                <tr>
                    <td>4</td>
                    <td><label>Channel ::*</label></td>
                    <td><input id="CHANNEL_ID" tabindex="4" maxlength="12"
                        size="12" name="CHANNEL_ID" autocomplete="off" value="WEB">
                    </td>
                </tr>
                <tr>
                    <td>5</td>
                    <td><label>txnAmount*</label></td>
                    <td><input title="TXN_AMOUNT" tabindex="10"
                        type="text" name="TXN_AMOUNT"
                        value="1">
                    </td>
                </tr>
                <tr>
                    <td></td>
                    <td></td>
                    <td><input value="CheckOut" type="submit"   onclick=""></td>
                </tr>
            </tbody>
        </table>
        * - Mandatory Fields
    </form>

Here is my pgRedirect.php file code

<?php
header("Pragma: no-cache");
header("Cache-Control: no-cache");
header("Expires: 0");
// following files need to be included
require_once("./lib/config_paytm.php");
require_once("./lib/encdec_paytm.php");

$checkSum = "";
$paramList = array();

$ORDER_ID = $_POST["ORDER_ID"];
$CUST_ID = $_POST["CUST_ID"];
$INDUSTRY_TYPE_ID = $_POST["INDUSTRY_TYPE_ID"];
$CHANNEL_ID = $_POST["CHANNEL_ID"];
$TXN_AMOUNT = $_POST["TXN_AMOUNT"];

// Create an array having all required parameters for creating checksum.
$paramList["MID"] = PAYTM_MERCHANT_MID;
$paramList["ORDER_ID"] = $ORDER_ID;
$paramList["CUST_ID"] = $CUST_ID;
$paramList["INDUSTRY_TYPE_ID"] = $INDUSTRY_TYPE_ID;
$paramList["CHANNEL_ID"] = $CHANNEL_ID;
$paramList["TXN_AMOUNT"] = $TXN_AMOUNT;
$paramList["WEBSITE"] = PAYTM_MERCHANT_WEBSITE;

/*
$paramList["CALLBACK_URL"] = "http://localhost/PaytmKit/pgResponse.php";
$paramList["MSISDN"] = $MSISDN; //Mobile number of customer
$paramList["EMAIL"] = $EMAIL; //Email ID of customer
$paramList["VERIFIED_BY"] = "EMAIL"; //
$paramList["IS_USER_VERIFIED"] = "YES"; //

*/

//Here checksum string will return by getChecksumFromArray() function.
$checkSum = getChecksumFromArray($paramList,PAYTM_MERCHANT_KEY);

?>
<html>
<head>
<title>Merchant Check Out Page</title>
</head>
<?php echo PAYTM_TXN_URL; 

?>

<body>
    <center><h1>Please do not refresh this page...</h1></center>
        <form method="post" action="<?php echo PAYTM_TXN_URL ?>" name="f1">
        <table border="1">
            <tbody>
            <?php
            foreach($paramList as $name => $value) {
                echo '<input type="hidden" name="' . $name .'" value="' . $value . '">';
            }
            ?>
            <input type="hidden" name="CHECKSUMHASH" value="<?php echo $checkSum ?>">
            </tbody>
        </table>
        <script type="text/javascript">
            document.f1.submit();
        </script>
    </form>
</body>
</html>

here is my config_paytm.php

<?php

define('PAYTM_ENVIRONMENT', 'TEST'); // PROD
define('PAYTM_MERCHANT_KEY', 'xxxxxxxxxxxxxxxxx'); //Change this constant's value with Merchant key received from Paytm.
define('PAYTM_MERCHANT_MID', 'xxxxxxxxxxxxxxxx'); //Change this constant's value with MID (Merchant ID) received from Paytm.
define('PAYTM_MERCHANT_WEBSITE', 'http://myurl/testd/paytm/index.php'); //Change this constant's value with Website name received from Paytm.

$PAYTM_STATUS_QUERY_NEW_URL='https://securegw-stage.paytm.in/merchant-status/getTxnStatus';
$PAYTM_TXN_URL='https://securegw-stage.paytm.in/theia/processTransaction';
if (PAYTM_ENVIRONMENT == 'PROD') {
    $PAYTM_STATUS_QUERY_NEW_URL='https://securegw.paytm.in/merchant-status/getTxnStatus';
    $PAYTM_TXN_URL='https://securegw.paytm.in/theia/processTransaction';
}

define('PAYTM_REFUND_URL', '');
define('PAYTM_STATUS_QUERY_URL', $PAYTM_STATUS_QUERY_NEW_URL);
define('PAYTM_STATUS_QUERY_NEW_URL', $PAYTM_STATUS_QUERY_NEW_URL);
define('PAYTM_TXN_URL', $PAYTM_TXN_URL);
?>