Losing 'sendto' variable after returning from payment gateway

[warriorkitty]

Hi all!

 

I'm creating a payment module for one payment gateway (PG in text). Now, after a successful pay inside PG, return url is www.my-site.com/checkout_process.php.

 

At the top, there are 3 if's:

if (!tep_session_is_registered('customer_id')) {
  $navigation->set_snapshot(array('mode' => 'SSL', 'page' => FILENAME_CHECKOUT_PAYMENT));
  tep_redirect(tep_href_link(FILENAME_LOGIN, '', 'SSL'));
}
if (!tep_session_is_registered('sendto')) {
  tep_redirect(tep_href_link(FILENAME_CHECKOUT_PAYMENT, '', 'SSL'));
}
if ( (tep_not_null(MODULE_PAYMENT_INSTALLED)) && (!tep_session_is_registered('payment')) ) {
  tep_redirect(tep_href_link(FILENAME_CHECKOUT_PAYMENT, '', 'SSL'));
}First *if* is OK (customer_id is present), but it fails on the second which redirects me to the checkout payment and doesn't do anything. Why isn't the 'sendto' variable registered anymore? I can confirm that it is registered before going to PG.

Thank you very much.