Code Samples. Each PayPal SDK includes sample code and apps available in Github to better help you understand how the APIs work. Note: The NVP/SOAP. PayPal PHP SDK is our official Open Source PHP SDK for supporting PayPal Rest APIs. Checkout all the supporting documents, samples, codebase from the. PayPal API Integration Tutorial - PayPal payment gateway integration in PHP with Sandbox and IPN. Example script to integrate PayPal.