I have visited related questions here but i need more specific answer.
I have hooked into the user registration form and i have added a custom submit handler for user registration before the user drupal core registration function.
I want to implement paid registration. I have visited Paypal IPN documentation but they said the require a return url.
Actually i am confused in the whole process. I want to know actual steps to implement payment api of paypal then if the user has paid the drupal core submit function should run otherwise i'll die the script.