I'm about to integrate automated payments into a site.

To date, I've successfully used paypal for a number of projects, but these have always been sites which sell physical goods, meaning I can upload the cart contents, user pays, person physically ships goods.

This site is a one off payment to enable extra features on a web app. My current thinking is to go down the paypal IPN route to get a notification back and update the users account based on the successful payment.

Question is in two parts: 1 - is there a better / simpler way? (any payment processor considered) 2 - does anyone know of a code library or plug in for php which will speed up my integration?

Thanks for your help.

Rob