How does WHMCS know which invoice to mark as being paid when a PayPal subscription payment comes in through the callback?
I see nothing in the callback POST data that indicates anything to which invoice should be marked as paid. Yet, they appear to get marked as paid.
Does it somehow tie together the custom field in the POST data?
I see nothing in the callback POST data that indicates anything to which invoice should be marked as paid. Yet, they appear to get marked as paid.
Does it somehow tie together the custom field in the POST data?