What is the right/recommended way to develop against of PayPal platform: Use the New PayPal SDK (https://www.x.com/developers/paypal/documentation-tools/paypal-sdk-index) Use the legacy PayPal SDK (which is quite old right now) Just send raw HTTPS requests following NVP protocol (in the end they are just REST-like API), and do not depend on any official API (just depend on the official NVP protocol description) Which one is considered the right way to go?