Best approach for multiple coupons?

Jason, I have followed this thread but haven't been able to activate multiple coupons at once; I have two that work independently of each other.

My question is this: I followed the eCart - "Adding coupons to your cart" tutorial and it created the eCart Set Session Value, which reads:

<?php
if (!session_id()) session_start();
if((((isset($_POST["txtPromoCode"]))?$_POST["txtPromoCode"]:"") != "")) {
$_SESSION["PromoCode"] = "".((isset($_POST["txtPromoCode"]))?$_POST["txtPromoCode"]:"") ."";
}
?>

In this thread, you advise on adding [] to the Session, in my case:


<?php
if (!session_id()) session_start();
if((((isset($_POST["txtPromoCode"]))?$_POST["txtPromoCode"]:"") != "")) {
$_SESSION["PromoCode"][] = "".((isset($_POST["txtPromoCode"]))?$_POST["txtPromoCode"]:"") ."";
}
?>

When I do make this change, the eCart Set Session Value in my server behaviours, disappears (?)

As for the custom expression trigger, I assume it is added to the end of the merchandising rule I created ... what is the separator - AND/OR? And, in this expression, the "coupon" variable for me would be PromoCode, or is it txtPromoCode in this case?

There is probably a simple logic to this that I am missing ... but I am close to the completion of my site, and my brain is rebelling a bit.