I'm having some trouble choosing between PayPal's Instant Payment Notification (IPN) and Payment Data Transfer (PDT). Basically, users buy a one-off product on my site, pay on PayPal, and return t...

I got error 4003 from paypal PDT when I was trying to retrieve payment information using the transaction ID. Although I there's a similar thread here : Paypal PDT error 4003 and I believe the answ...