Paypal Example:
https://www.paypal.com/cgi-bin/webscr?business=hacxx@gmail.com&currency_code=EUR&item_name=Hacxx%20Crypto%20Identifier%204%20%28CryptoDetectX%29&quantity=1&no_note=1&no_shipping=1&custom=iu6LC0Q94CbCgX53yDY3MyfWmn-kgDBd&charset=utf8&email=&return=&cancel_return=&notify_url=&cmd=_xclick-subscriptions&a3=20&p3=1&t3=M&src=1&sra=1

Note:
The link goes to Paypal.com and allow users to enter credit card details to finish the purchase.

Download:
https://link-center.net/68451/paypal-direct-shopping