Integration Guide

Third-Party Shopping Carts – The Cart Upload Command
Implementing the Instant Update API With the Cart Upload Command
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328 June 2012 PayPal Payments Standard Integration Guide
3. Before displaying the PayPal Review page, PayPal sends the buyer’s shipping address to
your callback server.
Every time the buyer changes the shipping address, PayPal calls your callback server.
4. Your callback server calculates tax, shipping, and insurance, based on the address in the
callback request.
Calculate the amounts in your own code, or request the shipping and insurance amounts
from your preferred carrier. If the address in the request is outside of the areas where you
ship, respond with NO_SHIPPING_OPTION_DETAILS set to 1.
5. PayPal updates the Review Your Payment page to show the options and rates that you sent
back in the callback response from your callback server.
6. The buyer makes final selections and clicks the Pay button.
7. PayPal displays a confirmation page, from which the buyer can click a link to print a
receipt.
Implementing Instant Update With the Cart Upload Command
You need a callback server to respond to Instant Update requests from PayPal. Also, you need
to add Instant Update HTML variables to your Cart Upload command to set up the checkout
for Instant Update.
1. Set up a secure server as your Instant Update callback server to accept Instant Update
requests from PayPal.
2. Develop you callback server to process Instant Update requests and respond with tax,
shipping, and insurance amounts.
3. Modify the HTML code of your Cart Upload commands by adding Instant Update HTML
variables:
– The URL of your callback server and the timeout duration
– Fallback tax, shipping options, and an insurance amount. You must specify at least 1
shipping option
– Dimensions for all individual items, if you base shipping rates on shipping dimensions
4. Eliminate your shipping options page.
5. Test your implementation of the callback and your fallback options.
The Review Your Payment Page After Implementing Instant Update
After you integrate the Instant Update API, you can display the shipping options, related
insurance options, and the tax amount. You control what to display, which is instantly updated
on the page.
The shipping options, related insurance options, and the tax amount appear on the page, as
follows: