the promo code form is set to use the GET method,
change the following code:
<?php
if (!session_id()) session_start();
if(isset($_POST["buttonPromo"])) {
$_SESSION["promoID"] = "".((isset($_GET["promoID"]))?$_GET["promoID"]:"") ."";
}
?>
to:
<?php
if (!session_id()) session_start();
if(isset($_GET["buttonPromo"])) {
$_SESSION["promoID"] = "".((isset($_GET["promoID"]))?$_GET["promoID"]:"") ."";
}
?>