Paypal ewp and php

I am trying to use to encrypt my paypal button for security purposes. I have used a site called http://www.stellarwe…yption_php.php. there example works fine but when I try to use my public certificate and private certificate and the certificate that paypal provides it will not process. I know that it is encoding my information but paypal keeps telling me “We were unable to decrypt the certificate id.” I am at a loss.

My code is as follows
If you have any ideas please respond

<HTML>
<?php
//Sample PayPal Button Encryption: Copyright 2006-2010 StellarWebSolutions.com
//Not for resale - license agreement at
//http://www.stellarwebsolutions.com/en/eula.php
//Updated: 2010 02 01

# private key file to use
$MY_KEY_FILE = "./patht/my-prvkey.pem";

# public certificate file to use
$MY_CERT_FILE = "./path/my-pubcert.pem";

# Paypal's public certificate
$PAYPAL_CERT_FILE = "./path/cert_key.pem";

# path to the openssl binary
$OPENSSL = "/usr/bin/openssl";


$form = array('cmd' => '_xclick',
'business' => 'xxx@xxx.com', //this is genric
'cert_id' => 'xxxxxxxxxxxxxx', // this is genric but i know the code I placed here is correct because I copied it directly from paypal.
'lc' => 'US',
'custom' => 'test',
'invoice' => '',
'currency_code' => 'USD',
'no_shipping' => '1',
'item_name' => 'Donation',
'item_number' => '1',
'amount' => '10'
);


$encrypted = paypal_encrypt($form);


function paypal_encrypt($hash)
{
//Sample PayPal Button Encryption: Copyright 2006-2010 StellarWebSolutions.com
//Not for resale - license agreement at
//http://www.stellarwebsolutions.com/en/eula.php
global $MY_KEY_FILE;
global $MY_CERT_FILE;
global $PAYPAL_CERT_FILE;
global $OPENSSL;


if (!file_exists($MY_KEY_FILE)) {
echo "ERROR: MY_KEY_FILE $MY_KEY_FILE not found\
";
}
if (!file_exists($MY_CERT_FILE)) {
echo "ERROR: MY_CERT_FILE $MY_CERT_FILE not found\
";
}
if (!file_exists($PAYPAL_CERT_FILE)) {
echo "ERROR: PAYPAL_CERT_FILE $PAYPAL_CERT_FILE not found\
";
}


//Assign Build Notation for PayPal Support
$hash['bn']= 'StellarWebSolutions.PHP_EWP2';

$data = "";
foreach ($hash as $key => $value) {
if ($value != "") {
//echo "Adding to blob: $key=$value\
";
$data .= "$key=$value\
";
}
}

$openssl_cmd = "($OPENSSL smime -sign -signer $MY_CERT_FILE -inkey $MY_KEY_FILE " .
"-outform der -nodetach -binary <<_EOF_\
$data\
_EOF_\
) | " .
"$OPENSSL smime -encrypt -des3 -binary -outform pem $PAYPAL_CERT_FILE";

exec($openssl_cmd, $output, $error);

if (!$error) {
return implode("\
",$output);
} else {
return "ERROR: encryption failed";
}
};
?>
<HEAD>
<LINK REL=stylesheet HREF="/styles/stellar.css" TYPE="text/css">
<TITLE>PHP Sample Donation using PayPal Encrypted Buttons</TITLE>
</HEAD>
<BODY bgcolor=white>
<TABLE border=0>
<TR><TD align=center>
<h1>Sample Donation Page</h1>
<P>This page uses encrypted PayPal buttons for your security.</P>
<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target=_blank>
<input type="hidden" name="cmd" value="_s-xclick">
<input type="hidden" name="encrypted" value="
<?PHP echo $encrypted; ?>">
<input type="submit" value="Donate $10">
</form>
<P><SMALL>(PayPal will open in a new window for demonstration purposes.)</SMALL></P>
</TD></TR></TABLE>
</BODY>

</HTML>