I did clarify where the code should go by saying:
add this code where you would like to display the error
I cont tell you exactly where the code should go in your page, it needs to be in the place of your page where you want the error to be displayed.
in design view, place your cursor where the error should go, the switch to code view and paste the code in.
you have changed the code for setting the real code session variable to use the value pf the promo code session:
<?php
if (!session_id()) session_start();
if("" == "") {
$_SESSION["RealCode"] = "".$_SESSION['PromoCode'] ."";
}
?>
it should be using the hard coded value MGPS:
<?php
if (!session_id()) session_start();
if("" == "") {
$_SESSION["RealCode"] = "MGPS";
}
?>