I've a subscription-based membership, however I encountered the following problem:
However as the user subscribed on May 1st 2012, he still has some days left if he were to cancel before one month. Any way to solve this? Does PayPal sends any IPN for this type of issue?
One solution I thought of is doing a cronjob every night to check if the month is up.
When we implemented subscription services on our own website, we basically handle the events like this:
Upon user sign in, we check whether the subscription has expired (which is easy if you store that in your db).
Basically, subscription events are separate from payment events. A subscription can be cancelled but that doesn't mean the payment gets refunded; that would be a separate event.
Btw, payment and subscription events can come in different order (e.g. payment can come first, followed by subscription notification); it's important to cater for that.