Integration Guide

Third-Party Shopping Carts – The Cart Upload Command
Implementing the Instant Update API With the Cart Upload Command
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332 June 2012 PayPal Payments Standard Integration Guide
 A new callback request is sent if the buyer changes the shipping address.
Example PayPal Review Page When You Do Not Ship to the Buyer’s Address
Setting Up the Callback for Instant Update
To set up the callback, establish a connection with PayPal by providing the location where
PayPal calls your callback server, along with your shipping options.
There are two sides to setting up the Instant Update callback:
 Establishing your Instant Update callback server
 Passing Instant Update callback information to PayPal
Establishing Your Instant Update Callback Server
To start, you must build and operate a secure, reliable, and fast callback server that computes
shipping options, corresponding insurance options, and tax, based on your business rules. To
verify that callback requests originate from PayPal.
The HTTP protocol to specify in your callback URL depends on the integration environment
you are using:
 The callback URL must start with HTTPS for production integration.
 The callback URL must start with HTTP or HTTPS for PayPal Sandbox integration.
Passing Instant Update Callback Information to PayPal
You pass Instant Update callback information in the HTML code of the Cart Upload
command. The Instant Update HTML variables let you specify the URL of you callback server
and the fallback values for shipping, insurance, and tax amounts.
To set up the Cart Upload command for Instant Update during the checkout experience, use at
a minimum the following Instant Update HTML variables:
 callback_url – the URL of your callback server
 callback_timeout – always use the value 3, unless instructed otherwise by PayPal