I'm trying to add another element to the $productArray array that's used in tpl_shopping_cart_default.php, and I thought it used the one created in includes/modules/pages/shopping_cart/header_php.php, but modifying that array (and even renaming it) doesn't seem to effect the cart page (doing a print_r() on the productArray to view elements). Where exactly can I make changes to the productArray array?

Thanks.