Integration Guide

Table Of Contents
Express Checkout Integration Guide October 2009 73
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 buyer’s 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
When implementing the Instant Update API, PayPal recommends that you follow best
practices.
Use the following best practices as a checklist as you integrate the 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 in “PayPal Review Page Order Details” on page 45.
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 default callback response time of 3 seconds.
z Follow PayPal-Defined Semantics and Syntax: Adhere to well-formed variable names
and syntax rules in the callback response to PayPal. If any errors occur in the response,
PayPal will use 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 the flat-rate shipping options
are used, you should honor the rates to ensure a consistent and good buyer experience.
z Localize Shipping Options: Return the localized shipping option labels based on the
buyers country and locale that PayPal sends in the callback request.