Hello I have a site where I want: A user logs in That user then click a "pay" button that goes to paypal They pay over paypal They return to a page on my site And somehow paypal tells me that they have paid. Paypal must in some way or another return the following values to my site ONCE they have paid: Their username (this can be sent when they click pay) A unique id (an md5 random hash) (sent when they pay) that relates the the username, so someone can't just return the value of their username themselves to page So basically, i want them to pay and then somehow work out if they actually did How can i do this? I am using php btw, but that shouldn't really matter, i am asking more about paypal side of thigns. And also if anyone has any thoughts about something i may have missed etc, lemme know Cheers edit - i found: https://www.paypal.com/uk/cgi-bin/webscr?cmd=p/pop/payment_data_transfer What token does it return to the script? And how do i turn it all into debug mode? Ie so there are no real payments, so i can test it all? Cheers