User selects a particular product on site 1 which proceeds to paypal purchase via a mid site 2. This paypal purchase button page is triggered by site 2 hosted on opencart. That means if paypal checks backlink it should only lead to site 2 and not site 1. That means user is passed on to paypal purchase page without landing on site 2 but in actual all purchase data exchange should be only between site 2 and paypal. After paypal confirmation is received by site 2 it should send back response to our reseller panel on [url removed, login to view] to generate voucher for specific product purchased and deliver it to users paypal email address.