Hi, we're working on a payment gateway system with PHP. We use sessions to store the shopping cart data. The system takes you off-site to the payment processor's site, and then return you to your site. On most hosts, we have no issues when we arrive back at our site and having the session data still be there. On those with an issue, turning off the PHP session referer_check has worked in the past. We don't really want to have to include the PHPSESSID as a GET variable, and hope to avoid that. What I'm looking for is what other server configurations would cause the session to be killed, and any other workarounds there might be.

Thanks for your help.