Integration Guide

Table Of Contents
PayPal Name-Value Pair API Basics
PayPal API Client-Server Architecture
3
28 May 2010 Express Checkout Integration Guide
PayPal Name-Value Pair API Requests and Responses
To perform a PayPal NVP API operation, you send an NVP-formatted request to a PayPal
NVP server and interpret the response.
In the following diagram, your website generates a request. The request is executed on a
PayPal server and the response is returned to your site.
The request identifies
z The name of the API operation to be performed and its version; for example,
SetExpressCheckout for version 62.0
z Credentials that identify the PayPal account making the request
z Request-specific information that controls the API operation to be performed
A PayPal API server performs the operation and returns a response. The response contains
z An acknowledgement status that indicates whether the operation was a success or failure
and whether any warning messages were returned
z Information that can be used by PayPal to track execution of the API operation
z Response-specific information required to fulfill the request
Multiple API Operations
Some of the features, such as Express Checkout, require you to call multiple API operations.
Typically, these features require you to
1. Invoke an API operation, such as SetExpressCheckout, that sets up the return URL to
which PayPal redirects your buyer’s browser after the buyer finishes on PayPal. Other
setup also can be performed by this API operation.
2. Invoke additional API operations after receiving the buyers permission on PayPal, for
example, GetExpressCheckoutDetails or DoExpressCheckoutPayment.
The following diagram shows the execution flow between your site and PayPal: