PayPal IPN: custom field not passing to IPN - paypal-ipn

Question

I have a paypal buy button that looks like this:
<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="business" value="my#email.com">
<input type="hidden" name="cmd" value="_cart">
<input type="hidden" name="upload" value="1">
<input type="hidden" name="item_name_1" value="item1">
<input type="hidden" name="amount_1" value="3">
<input type="hidden" name="item_name_2" value="item2">
<input type="hidden" name="amount_2" value="5">
<input type="hidden" name="custom" value="Admin|2">
<input type="hidden" name="discount_rate_cart" value="5">
<input type="hidden" name="notify_url" value="paypal-ipn.php">
<input type="hidden" name="currency_code" value="EUR">
<input type="hidden" name="return" value="Thank-you-page">
<input type="hidden" name="country" value="SE">
<input type="submit" value="Checkout" id="checkoutButton">
</form>
And a IPN that looks like this:
<?php
session_start();
// STEP 1: read POST data
// Reading POSTed data directly from $_POST causes serialization issues with array data in the POST.
// Instead, read raw POST data from the input stream.
$raw_post_data = file_get_contents('php://input');
$raw_post_array = explode('&', $raw_post_data);
$myPost = array();
foreach ($raw_post_array as $keyval)
{
$keyval = explode ('=', $keyval);
if (count($keyval) == 2)
{
$myPost[$keyval[0]] = urldecode($keyval[1]);
}
}
// read the IPN message sent from PayPal and prepend 'cmd=_notify-validate'
$req = 'cmd=_notify-validate';
if(function_exists('get_magic_quotes_gpc'))
{
$get_magic_quotes_exists = true;
}
foreach ($myPost as $key => $value)
{
if($get_magic_quotes_exists == true && get_magic_quotes_gpc() == 1)
{
$value = urlencode(stripslashes($value));
}
else
{
$value = urlencode($value);
}
$req .= "&$key=$value";
}
// Step 2: POST IPN data back to PayPal to validate
$ch = curl_init('https://www.paypal.com/cgi-bin/webscr');
curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: Close'));
// In wamp-like environments that do not come bundled with root authority certificates,
// please download 'cacert.pem' from "http://curl.haxx.se/docs/caextract.html" and set
// the directory path of the certificate as shown below:
// curl_setopt($ch, CURLOPT_CAINFO, dirname(__FILE__) . '/cacert.pem');
if( !($res = curl_exec($ch)) )
{
// error_log("Got " . curl_error($ch) . " when processing IPN data");
curl_close($ch);
exit;
}
curl_close($ch);
if(strcmp($res, "VERIFIED") == 0)
{
// The IPN is verified, process it:
// check whether the payment_status is Completed
// check that txn_id has not been previously processed
// check that receiver_email is your Primary PayPal email
// check that payment_amount/payment_currency are correct
// process the notification
// assign posted variables to local variables
$custom = explode('|', $_POST['custom']);
$user = $custom['0'];
$itemAmount = $custom['1'];
$item_name = "";
for($i = 0 ; $i < $itemAmount ; $i++)
{
$item_name .= $_POST['item_name_' . ($i + 1)] . '<br>';
}
$payment_status = $_POST['payment_status'];
$payment_amount = $_POST['mc_gross'] . ' ' . $_POST['mc_currency'];
$txn_id = $_POST['txn_id'];
$receiver_email = $_POST['receiver_email'];
$payer_email = $_POST['payer_email'];
$accstatus = $_POST['payer_status'];
include("../config.php");
$sql = "INSERT INTO `purchase` (`product`,`member`,`amount`,`ppmail`,`accstatus`,`status`)
VALUES
('$item_name','$user','$payment_amount','$payer_email','$accstatus','$payment_status')";
if (!mysql_query($sql,$con))
{
die('Error: ' . mysql_error());
}
$post_data_string = serialize($_POST);
mail('mail#domain.com', 'PayPal IPN', $post_data_string);
mysql_close($con);
// IPN message values depend upon the type of notification sent.
// To loop through the &_POST array and print the NV pairs to the screen:
foreach($_POST as $key => $value)
{
echo $key." = ". $value."<br>";
}
}
else if(strcmp($res, "INVALID") == 0)
{
// IPN invalid, log for manual investigation
echo "The response from IPN was: <b>" .$res ."</b>";
}
?>
Now why does not the custom field get passed on to the API?
I do get this in error logging, because custom[0] = "" and custom[1] does not exist:
HP Notice: Undefined offset: 1 in /home1/planetzi/public_html/firefallcrystite/action/paypal-ipn.php on line 79