getting paypal ipn notification without confirmation of the user?

how can i get paypal ipn notification without user clicking on the开发者_JS百科 "return to merchant" link?

how can i make it so when the transaction is complete i get the notification?

i also have an unrelated question

how can i check which user made the payment? surely not with there email/name is there a way to uniquely identify each user?

i am on wordpress, using php

The Instant Payment Notification (IPN) of paypal calls a script on your server and transmit all payment information as $_POST-variables.

You have to give the user an unique hashid and send it along by redirecting the user to paypal. The user pays your products and after a successful payment he can return to your merchant and your script is called by paypal.

Here you can create your own script for IPN: https://www.paypaltech.com/SG2/

You will be notified after a successful payment. It's not relevant whether the user returns to your merchant or not.

Some more information for IPN:

https://www.paypalobjects.com/en_US/ebook/PP_OrderManagement_IntegrationGuide/Appx_ipn_and_pdt_variables.html

https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_html_IPNandPDTVariables

and the paypal developer network: http://www.x.com