I have a site that needs a PayPal integration.
I will post to the page that contains the paypal now button username, password and amount of $ to bill > next page is the paypal buy now button > paypal page > confirmation page back on my site > a IPN php file that tells me the username, password and amount of $ that were paid (username, password are sent when starting the purchase) in PHP variables.
Basically I will communicate with 2 PHP files: I will send 3 variables to one of them > the user is directed to the paypal buy now page and the IPN where I get 3 variables only if the payment is confirmed. (you may create more than 2 files).
I will also need instructions on setting up my paypal e-mail there, welcome page URL, declined page URL, paypal IPN URL, etc.