I have a complete automatic notification system running on my web page, that is a simple PHP script which search for emails in a database and then send an email to each one, all of this using a Cronjob. The thing is that now i want to transform my free service into a pay one. I want to use PayPal, for a while I've been using it for donations, but now i want it to do monthly payments, and every time the user pays a month a new value enter in the database so the PHP script can know if the user pay or not in order to send or not the email.
I know how to use the monthly payment system on PayPal, but I can't find any tutorials on how to integrate the checkout process of PayPal to my custom made php script in order to automatically know when my users pays and then do a modification on MySQL. Thanks
