Download PayPal Website Payments Standard - 2012 Integration Guide

Third-Party Shopping Carts – The Cart Upload Command
Implementing the Instant Update API With the Cart Upload Command
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Here is how the Instant Update API works:
1. When a buyer logs in to PayPal, the PayPal server calls your callback server with the
buyer’s default shipping address, which is stored in the PayPal system.
2. Your callback server responds with the shipping options available for that address, along
with any insurance options and tax adjustments on the order.
3. PayPal displays this information on the Review your information page so buyers can
choose from the options.
How Instant Update Works With the Cart Upload Command
The figure below shows how the Instant Update callback works in the Cart Upload checkout
experience.
How Instant Update Works in the Cart Upload Checkout Experience
The checkout experience proceeds from left to right. Numbered events in the illustration above
are described below.
1. The checkout experience begins when a buyer clicks the checkout button on the Shopping
Cart page of your third-party cart.
In the HTML code of the checkout button, provide the URL where PayPal can call your
callback server, as well as fallback tax, shipping and insurance amounts. If you or your
carrier base shipping rates on shipment size, include the shippping dimension HTML
variables on individual items in the cart.
2. The buyer is redirected to PayPal to enter billing information or to log in to PayPal.
PayPal Payments Standard Integration Guide
June 2012
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