Direct Payment Direct Payment API is not a stand-alone product. You are required to use Direct Payment API and Express Checkout together as part of the Website Payments Pro solution 1. Transactions are sent over the internet using Secure Socket Layer (SSL) 2. You must also retrieve the IP address of the buyer's browser and include this with the request. 3. When a buyer clicks the Pay button, invoke the DoDirectPayment API operation. 4. The PayPal API server executes the request and returns a response. • Ack code (Success, SuccessWithWarning, or Failure) • Amount of the transaction • AVS response code • CSC response code • PayPal transaction ID • Error codes and messages (if any) • Correlation ID (unique identifier for the API call) 5. If the operation is successful, you send the buyer to an order confirmation page. The Ack code determines whether the operation is a success. • If successful, you should display a message on the order confirmation page. • Otherwise, you should show the buyer information related to the error. You should also provide an opportunity to pay using a different payment method. ---- PCI compliant You are responsible for processing card industry (PCI) compliance for protecting cardholder data. For example, storing the Card Security Code (CSC ) violates PCI compliance. For more information about PCI compliance, see PCI Security Standards Council. 具体的你看你pro账户里面的文档,有专门针对developer的 另外不一定要选择paypal,paypal的fee贵,而且review多