[SOLVED] 'sorry some error occurred' while integrating PayUMoney payment gateway in Test mode

I'm trying to integrate PayUMoney payment gateway in my client site. My client provided me the login details of PayUMoney. I was able to locate the Merchant Key but cannot find either of the two:
Merchant Salt
Developer site where I can create a test account and test on sandbox
PayUMoney provided me a form with some default value but when I test, it gives the message: sorry some error occurred.
Here is the form:
<?php
// Merchant key here as provided by Payu
$MERCHANT_KEY = "JBZaLc";

// Merchant Salt as provided by Payu
$SALT = "GQs7yium";

// End point - change to https://secure.payu.in for LIVE mode
$PAYU_BASE_URL = "https://test.payu.in";

$action = '';

$posted = array();
if(!empty($_POST)) {
//print_r($_POST);
foreach($_POST as $key => $value) {    
$posted[$key] = $value; 

}
}

$formError = 0;

if(empty($posted['txnid'])) {
// Generate random transaction id
$txnid = substr(hash('sha256', mt_rand() . microtime()), 0, 20);
} else {
$txnid = $posted['txnid'];
}
$hash = '';
// Hash Sequence
$hashSequence =     "key|txnid|amount|productinfo|firstname|email|udf1|udf2|udf3|udf4|udf5|udf6|udf7|udf8|udf9|udf10";
if(empty($posted['hash']) && sizeof($posted) > 0) {
if(
      empty($posted['key'])
      || empty($posted['txnid'])
      || empty($posted['amount'])
      || empty($posted['firstname'])
      || empty($posted['email'])
      || empty($posted['phone'])
      || empty($posted['productinfo'])
      || empty($posted['surl'])
      || empty($posted['furl'])
      || empty($posted['service_provider'])
) {
$formError = 1;
} else {
//$posted['productinfo'] = json_encode(json_decode('[{"name":"tutionfee","description":"","value":"500","isRequired":"false"},{"name":"developmentfee","description":"monthly tution     fee","value":"1500","isRequired":"false"}]'));
$hashVarsSeq = explode('|', $hashSequence);
$hash_string = '';  
foreach($hashVarsSeq as $hash_var) {
  $hash_string .= isset($posted[$hash_var]) ? $posted[$hash_var] : '';
  $hash_string .= '|';
}

$hash_string .= $SALT;


$hash = strtolower(hash('sha512', $hash_string));
$action = $PAYU_BASE_URL . '/_payment';
}
} elseif(!empty($posted['hash'])) {
$hash = $posted['hash'];
$action = $PAYU_BASE_URL . '/_payment';
}
?>
<html>
<head>
<script>
var hash = '<?php echo $hash ?>';
function submitPayuForm() {
  if(hash == '') {
    return;
  }
  var payuForm = document.forms.payuForm;
  payuForm.submit();
}
</script>
</head>
<body onLoad="submitPayuForm()">
<h2>PayU Form</h2>
<br/>
<?php if($formError) { ?>
  <span style="color:red">Please fill all mandatory fields.</span>
  <br/>
  <br/>
<?php } ?>
<form action="<?php echo $action; ?>" method="post" name="payuForm">
  <input type="hidden" name="key" value="<?php echo $MERCHANT_KEY ?>" />
  <input type="hidden" name="hash" value="<?php echo $hash ?>"/>
  <input type="hidden" name="txnid" value="<?php echo $txnid ?>" />
  <table>
    <tr>
      <td><b>Mandatory Parameters</b></td>
    </tr>
    <tr>
      <td>Amount: </td>
      <td><input name="amount" value="<?php echo (empty($posted['amount'])) ? '' : $posted['amount'] ?>" /></td>
      <td>First Name: </td>
      <td><input name="firstname" id="firstname" value="<?php echo (empty($posted['firstname'])) ? '' : $posted['firstname']; ?>" /></td>
    </tr>
    <tr>
      <td>Email: </td>
      <td><input name="email" id="email" value="<?php echo (empty($posted['email'])) ? '' : $posted['email']; ?>" /></td>
      <td>Phone: </td>
      <td><input name="phone" value="<?php echo (empty($posted['phone'])) ? '' : $posted['phone']; ?>" /></td>
    </tr>
    <tr>
      <td>Product Info: </td>
      <td colspan="3"><textarea name="productinfo"><?php echo (empty($posted['productinfo'])) ? '' : $posted['productinfo'] ?></textarea></td>
    </tr>
    <tr>
      <td>Success URI: </td>
      <td colspan="3"><input name="surl" value="<?php echo (empty($posted['surl'])) ? '' : $posted['surl'] ?>" size="64" /></td>
    </tr>
    <tr>
      <td>Failure URI: </td>
      <td colspan="3"><input name="furl" value="<?php echo (empty($posted['furl'])) ?     '' : $posted['furl'] ?>" size="64" /></td>
    </tr>

    <tr>
      <td>Service Provider: </td>
      <td colspan="3"><input name="service_provider" value="<?php echo (empty($posted['service_provider'])) ? '' : $posted['service_provider'] ?>" size="64" /></td>
    </tr>

    <tr>
      <td><b>Optional Parameters</b></td>
    </tr>
    <tr>
      <td>Last Name: </td>
      <td><input name="lastname" id="lastname" value="<?php echo (empty($posted['lastname'])) ? '' : $posted['lastname']; ?>" /></td>
      <td>Cancel URI: </td>
      <td><input name="curl" value="" /></td>
    </tr>
    <tr>
      <td>Address1: </td>
      <td><input name="address1" value="<?php echo (empty($posted['address1'])) ? '' : $posted['address1']; ?>" /></td>
      <td>Address2: </td>
      <td><input name="address2" value="<?php echo (empty($posted['address2'])) ? '' : $posted['address2']; ?>" /></td>
    </tr>
    <tr>
      <td>City: </td>
      <td><input name="city" value="<?php echo (empty($posted['city'])) ? '' : $posted['city']; ?>" /></td>
      <td>State: </td>
      <td><input name="state" value="<?php echo (empty($posted['state'])) ? '' : $posted['state']; ?>" /></td>
    </tr>
    <tr>
      <td>Country: </td>
      <td><input name="country" value="<?php echo (empty($posted['country'])) ? '' : $posted['country']; ?>" /></td>
      <td>Zipcode: </td>
      <td><input name="zipcode" value="<?php echo (empty($posted['zipcode'])) ? '' : $posted['zipcode']; ?>" /></td>
    </tr>
    <tr>
      <td>UDF1: </td>
      <td><input name="udf1" value="<?php echo (empty($posted['udf1'])) ? '' : $posted['udf1']; ?>" /></td>
      <td>UDF2: </td>
      <td><input name="udf2" value="<?php echo (empty($posted['udf2'])) ? '' : $posted['udf2']; ?>" /></td>
    </tr>
    <tr>
      <td>UDF3: </td>
      <td><input name="udf3" value="<?php echo (empty($posted['udf3'])) ? '' : $posted['udf3']; ?>" /></td>
      <td>UDF4: </td>
      <td><input name="udf4" value="<?php echo (empty($posted['udf4'])) ? '' : $posted['udf4']; ?>" /></td>
    </tr>
    <tr>
      <td>UDF5: </td>
      <td><input name="udf5" value="<?php echo (empty($posted['udf5'])) ? '' : $posted['udf5']; ?>" /></td>
      <td>PG: </td>
      <td><input name="pg" value="<?php echo (empty($posted['pg'])) ? '' : $posted['pg']; ?>" /></td>
    </tr>
    <tr>
      <?php if(!$hash) { ?>
        <td colspan="4"><input type="submit" value="Submit" /></td>
      <?php } ?>
    </tr>
  </table>
</form>
</body>
</html>