paypal store user data to database - php

Question

I have a website with account system. I am selling some services. I am using a paypal dynamic subscription button for selling. My question is how do I know, when the IPN is sent back from paypal, what user made the payment? I have a working script that sends the payment info to paypal and another script that receives the info back from paypal and inserts it into the database, but I don't know how to know what user sent the payment. I am looking for an idea on how to accomplish this.
Send button:
<form name="_xclick" action="https://www.sandbox.paypal.com/cgi-bin/webscr method="post">
<input type="hidden" name="cmd" value="_xclick-subscriptions">
<input type="hidden" name="business" value="user#example.com">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="no_shipping" value="1">
<input type="image" src="http://www.paypal.com/en_US/i/btn/btn_subscribe_LG.gif" border="0" name="submit" alt="Make payments with PayPal - it's fast, free and secure!">
<input type="hidden" name="a3" value="<?php echo $pay_value; ?>">
<input type="hidden" name="p3" value="1">
<input type="hidden" name="t3" value="M">
<input type="hidden" name="src" value="1">
<input type="hidden" name="sra" value="1">
</form>
ipn script:
<?php
// tell PHP to log errors to ipn_errors.log in this directory
ini_set('log_errors', true);
ini_set('error_log', dirname(__FILE__).'/ipn_errors.log');
// intantiate the IPN listener
include('include/ipnlistener.php');
include('include/conn.php');
$listener = new IpnListener();
// tell the IPN listener to use the PayPal test sandbox
$listener->use_sandbox = true;
// try to process the IPN POST
try {
$listener->requirePostMethod();
$verified = $listener->processIpn();
} catch (Exception $e) {
error_log($e->getMessage());
exit(0);
}
if ($verified) {
$errmsg = ''; // stores errors from fraud checks
// Make sure the payment status is "Completed"
if ($_POST['payment_status'] != 'Completed') {
}
exit(0);
}
if ($_POST['txn_type'] == 'subscr_eot') {
$link = mysql_connect($conn_host,$conn_user,$conn_pass) or die('Connection to mysql failed!');
mysql_select_db($conn_db,$link) or die('Connection to database failed!');
$sql = mysql_query("UPDATE user_data SET paid='0.00' WHERE uid='$userID'");
mysql_close($link);
if (!empty($errmsg)) {
// manually investigate errors from the fraud checking
$body = "IPN failed fraud checks: \n$errmsg\n\n";
$body .= $listener->getTextReport();
mail('user#example.com', 'IPN Fraud Warning', $body);
} else {
$link = mysql_connect($conn_host,$conn_user,$conn_pass) or die('Connection to mysql failed!');
mysql_select_db($conn_db,$link) or die('Connection to database failed!');
$sql = mysql_query("UPDATE user_data SET paid='$paid' WHERE uid='$userID'");
mysql_close($link);
}
} else {
// manually investigate the invalid IPN
mail('user#example.com', $listener->getTextReport());
}
?>

Answer 1

You can send the encrypted user id in the form as custom variable
<input type="hidden" name="custom" value="put user id here " />
The IPN will send you this custom code back, so that you can update your database.
you will get the value using $_POST['custom'] in your IPN validation page.
Please find the complete set of variables below.
<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_xclick-subscriptions">
<input type="hidden" name="business" value="nora#paypal.com">
<input type="hidden" name="item_name" value="Baseball Hat Monthly">
<input type="hidden" name="item_number" value="123">
<input type="hidden" name="image_url" value="https://www.yoursite.com/logo.gif">
<input type="hidden" name="no_shipping" value="1">
<input type="hidden" name="return" value="http://www.yoursite.com/thankyou.htm">
<input type="hidden" name="cancel_return" value="http://www.yoursite.com/cancel.htm">
<input type="hidden" name="a1" value="0">
<input type="hidden" name="p1" value="1">
<input type="hidden" name="t1" value="W">
<input type="hidden" name="a2" value="5.00">
<input type="hidden" name="p2" value="2">
<input type="hidden" name="t2" value="M">
<input type="hidden" name="a3" value="50.00">
<input type="hidden" name=”p3" value="1">
<input type="hidden" name="t3" value="Y">
<input type="hidden" name="src" value="1">
<input type="hidden" name="sra" value="1">
<input type="hidden" name="srt" value="5">
<input type="hidden" name="no_note" value="1">
<input type="hidden" name="custom" value="customcode">
<input type="hidden" name="invoice" value="invoicenumber">
<input type="hidden" name="usr_manage" value="1">
<input type="image" src="http://images.paypal.com/images/x-click-but01.gif" border="0" name="submit" alt="Make payments with PayPal - it’s fast, free and secure!">
I hope this helps.
Thanks.