Integration Guide

Table Of Contents
Express Checkout Integration Guide May 2010 81
Implementing the Instant Update API
Following Instant Update API Best Practices
7
4. The buyer is redirected to PayPal.
5. When the buyer first logs in to the PayPal site, PayPal obtains the buyers shipping address
and sends it in the callback request (red down arrow) to your callback server at the
specified URL.
NOTE: If the buyer changes their shipping address on the PayPal Review page, PayPal
will make subsequent calls to the callback request.
6. You respond to the callback (red up arrow) with the shipping option rates based on the
buyers shipping address. You can also adjust the tax amount and send insurance options.
Depending on your business processes, you may send an API call to your carrier to
calculate the rates and options based on the shipping address.
7. PayPal updates the Review Page to show the options and rates based on your response.
8. The buyer makes final selections and clicks Continue.
9. You must call GetExpressCheckoutDetails to obtain the buyers final shipping
option selections.
10. You call DoExpressCheckoutPayment to perform the transaction.
Following Instant Update API Best Practices
PayPal recommends its list of best practices as a checklist for completing your implementation
of the Instant Update API.
z Meet the pre-requisites – Provide order line-item details to take advantage of the Instant
Update API. The example in this document uses the order line-item details example
described PayPal Review Page Order Details.
z Streamline the checkout flow – Existing partners and merchants with Express Checkout
integrations can eliminate the current shipping options page.
z Use the default callback timeout – Use the recommended 3-second callback response
timeout.
z Follow PayPal-defined semantics and syntax – Adhere to well-formed variable names
and syntax rules in the callback response to PayPal. If errors occur in the response, PayPal
uses the flat-rate shipping options.
z Call GetExpressCheckoutDetails – You must call GetExpressCheckoutDetails to
find out what options the buyer selected on the PayPal Review page.
z Ensure a consistent and good buyer experience – When flat-rate shipping options are
used, you should honor the rates to ensure a consistent and good buyer experience.
z Localize shipping options – Return localized shipping options, based on the buyers
country and locale, which PayPal sends in the callback request.