Configure PayPal with Instant Payment Notification

1- Login to your PayPal Business Account
2- Go My Account -> Profile -> My selling tools
3- Click update on Website preferences
4- Choose off for Auto Return and remove the url inside

5- Choose off for Payment Data Transfer

6- Click save button

7- Go to Instant Payment Notification Preferences
8- Enable IPN message -> Pass your notification URL

9- Save

More detail about IPN

1- https://developer.paypal.com/docs/classic/ipn/integration-guide/IPNIntro/

2- https://github.com/paypal/ipn-code-samples

3- https://developer.paypal.com/docs/classic/ipn/integration-guide/IPNandPDTVariables/

4- https://www.paypal.com/kh/cgi-bin/webscr?cmd=p/acc/ipn-subscriptions-outside