I'm trying to sell something to domain owners. I need to know their domain names. Before the payment procedure I'll ask their domain names in my web site, I'll store the data in the cookies or the url, then I want to pass the data (domain name) to the PayPal so that I'll know who paid for what domain name. I know PHP and HTML in advanced level but I don't know how to pass the data to PayPal. How I'll do that?

Thanks in advance!