Integration Guide

Table Of Contents
Implementing the Instant Update API
How the Callback Works in the Express Checkout Flow
7
80 May 2010 Express Checkout Integration Guide
How the Callback Works in the Express Checkout Flow
The figure below shows how the callback integrates into the Express Checkout flow.
Callback integrated into Express Checkout flow
From left to right, the following events are represented. Text in boldface describes events
supporting the callback.
1. The Express Checkout flow is initiated on your shopping cart page when the buyer clicks
the Checkout with PayPal button.
2. In the call to the SetExpressCheckout API operation, you provide the URL where
PayPal can call your callback server, the flat-rate shipping options, and cart line-item
details.
3. You receive a token in the response.