Hello , How do sites like ptc sites send instant payments to paypal ? does somebody work to send money and instantly or its just scripts ? If its scripts how it works ?
Paypal business accounts have features like that, there's a forum from inside Paypal where you can read all about merchant programming and even request help from Paypal's own development team.
Login to your paypal account (Premier or Business) and go Profile>Instant Payment Notification. You will find the answer you are looking for there.