I am preparing to start a network of websites that will require registration to run be able to use them. For example, lets say I have 10 websites... All the login and registration scripts will report back to a single sql database and enter the new user information. The main site has a paypal ipn.php file to update if a user paid or not.... If I have 10 domains and a user makes a payment from each domain, will paypal send that data to the main ipn.php for the site? Paypal only allows one ipn of course. Basically I need to have it so no matter what domain is sending the payment, paypal will send the data to that single ipn.