Allow Scrobbl'd to communicate with my website to confirm when a payment recieved for an Invoice ID
This would mean once Scrobbl'd detects a payment has been completed my PHP script can run a series of tasks such as adding the user to our premium members database based on the total of the sale, etc.
I guess this might form some sort of a Scrobbld API — it’s something that we’ve been considering but is obviously quite a bit of work. In the meantime, could I suggest that you look at IPN? We’ve done a few blog posts on it — http://blog.scrobbld.com/paypal/paypal-instant-payment-notification-and-php/ and http://blog.scrobbld.com/paypal/the-paypal-api-and-php/. You do have to mess around with a bit of verification, but it’s not too tough. You can forward IPNs that Scrobbld receives to your website, so you could probably just check that Scrobbld is the referrer, and then check the price. If you need a hand just shoot me an email at ian [at] scrobbld.com.