authorize.net SIM code worked with php4 but not with PHP Version 5.2.9

<?php
// This sample code requires the mhash library for PHP versions older than
// 5.1.2 - http://hmhash.sourceforge.net/
	
// the parameters for the payment can be configured here
// the API Login ID and Transaction Key must be replaced with valid values
$loginID		= "xxx";
$transactionKey = "xxx";
$amount 		= "19.99";
$description 	= "Sample Transaction";
$label 			= "Confirm Amount and Continue"; // The is the label on the 'submit' button
$testMode		= "false";
// By default, this sample code is designed to post to our test server for
// developer accounts: https://test.authorize.net/gateway/transact.dll
// for real accounts (even in test mode), please make sure that you are
// posting to: https://secure.authorize.net/gateway/transact.dll
$url			= "https://secure.authorize.net/gateway/transact.dll";
 
// If an amount or description were posted to this page, the defaults are overidden
if ($_REQUEST["amount"])
	{ $amount = $_REQUEST["amount"]; }
if ($_REQUEST["description"])
	{ $description = $_REQUEST["description"]; }
 
// an invoice is generated using the date and time
$invoice	= date(YmdHis);
// a sequence number is randomly generated
$sequence	= rand(1, 1000);
// a timestamp is generated
$timeStamp	= time ();
 
// The following lines generate the SIM fingerprint.  PHP versions 5.1.2 and
// newer have the necessary hmac function built in.  For older versions, it
// will try to use the mhash library.
if( phpversion() >= '5.1.2' )
{	$fingerprint = hash_hmac("md5", $loginID . "^" . $sequence . "^" . $timeStamp . "^" . $amount . "^", $transactionKey); }
else 
{ $fingerprint = bin2hex(mhash(MHASH_MD5, $loginID . "^" . $sequence . "^" . $timeStamp . "^" . $amount . "^", $transactionKey)); }
 
// Print the Amount and Description to the screen.
echo "Amount: $amount <br /> <br />";
// echo "Description: $description <br />";
 
// Create the HTML form containing necessary SIM post values
echo "<FORM method='post' action='$url' >";
// Additional fields can be added here as outlined in the SIM integration guide
// at: http://developer.authorize.net
echo "	<INPUT type='hidden' name='x_login' value='$loginID' />";
echo "	<INPUT type='hidden' name='x_amount' value='$amount' />";
echo "	<INPUT type='hidden' name='x_description' value='$description' />";
echo "	<INPUT type='hidden' name='x_invoice_num' value='$invoice' />";
echo "	<INPUT type='hidden' name='x_fp_sequence' value='$sequence' />";
echo "	<INPUT type='hidden' name='x_fp_timestamp' value='$timeStamp' />";
echo "	<INPUT type='hidden' name='x_fp_hash' value='$fingerprint' />";
echo "	<INPUT type='hidden' name='x_test_request' value='$testMode' />";
echo "	<INPUT type='hidden' name='x_show_form' value='PAYMENT_FORM' />";
echo "	<input type='submit' value='$label' />";
echo "</FORM>";
?>