The PayPal module, "PayPal IPN - Website Payments Standard" is a popular Zen Cart™ payment module.

Using this with Cartage can cause problems, due to the nature of the Javascript that resizes the iframe. As a security feature, browsers will not run a script in another window (such as the parent) if the domain is different. This is the cause of some issues with Cartage, but when PayPal is involved it can cause some serious issues. In some situations, the submit / confirm button will not show as the iframe (which is now displaying a PayPal page) is too short.

We have gotten around this by changing the Zen Cart™ file
includes/templates/template_default/templates/tpl_checkout_confirmation_default.php page.

Line 174 currently reads:

echo zen_draw_form(‘checkout_confirmation’, $form_action_url, ‘post’, ‘id=”checkout_confirmation” onsubmit=”submitonce();”’);

The amended code is:

//NOVEDIT: Paypal needs to load outsite iframe
$lsEscapeFrame = (strstr($form_action_url, HTTPS_SERVER)) ? ’’ : ‘target=”_parent”’;
echo zen_draw_form(‘checkout_confirmation’, $form_action_url, ‘post’, $lsEscapeFrame.’ id=”checkout_confirmation” onsubmit=”submitonce();”’);

The modified file is contained in this zip. As always, make backups before starting, and using the override template ability of Zen Cart. In other words, don't override the existing file, instead put it in your Cartage template folder. If you are using Cartage as the template, this is the folder to place the file in: includes/templates/template_default/cartage/