Ensure paypal return page coming from Paypal

Further to my question and awesome answers from the previous thread, Redirection / Return Check in PHP

I would also love to know, if a payment confirmation page is returned to my website from PayPal, how can I 100% sure that it is co开发者_开发问答ming from paypal and the payment is made?

Regards, Andy

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To make sure the request is coming from PayPal you can try resolving the IP address:

if (preg_match('~^(?:.+[.])?paypal[.]com$~', gethostbyaddr($_SERVER['REMOTE_ADDR'])) > 0)
{
    // came from PayPal
}

You can (and should) also request https://www[.sandbox].paypal.com/cgi-bin/webscr/ with the same data your received in POST and append the cmd => _notify-validate key-value pair to the request, if the response is VERIFIED the data is valid.

See also this question: PayPal IPN Security