Developer's Guide
Table Of Contents
Website Payments Pro Developer’s Guide 49
PayPal Express Checkout Transaction Processing
Sale and Authorisation Transactions
6
The web page layout may differ somewhat from your own web design, but the points at which
the PayPal Express Checkout API calls are made and when the customer is redirected to
PayPal and back to your website are important to understand. The events that take place at
each numbered step in the figure are described below:
1. On your website when your customer chooses to pay with PayPal, you submit a Set
Express Checkout request.
2. The server sends back a token, a string value to track your customer throughout the
checkout process.
3. You direct your customer to the PayPal site, where they log in, select a funding source, and
confirm contact and postal information. PayPal Express Checkout includes parameters that
you can use to customise the PayPal pages so they match characteristics of your own
website. For example, you can provide your own logo and colours. These parameters are
described in “Set Express Checkout Request Parameters” on page 53.
4. When your customer clicks the “Continue” button, PayPal sends them back to your site at
the return URL you specified in the Set Express Checkout request. The token is appended
to the URL to identify the customer.
5. Optionally you can send the Get Express Checkout Details request to obtain details about
your customer such as the customer’s telephone number and postal address. You send the
token to identify the customer. The server returns the requested information.
6. When your customer clicks the “Pay” button, you submit the Do Express Checkout
Payment request to perform the actual payment transaction. The server returns the
transaction result.
Sale and Authorisation Transactions
PayPal Express Checkout Sale and Authorisation transactions are handled a little differently
than described in Chapter 4, “Performing Direct Payment Credit Card Transactions.” Unlike a
Direct Payment credit card Sale or Authorisation transaction request, which is submitted as a
single request, a PayPal Express Checkout Sale or Authorisation requires that you submit at
least two requests:
z Set Express Checkout
z Do Express Checkout
(A third request, Get Express Checkout Details, is optional.)
Do Express Checkout performs the actual money transfer. The Set Express Checkout and Get
Express Checkout Details requests provide supporting data. To distinguish between a Sale or
Authorisation request, you must pass an additional ACTION parameter with the respective
value, S or G. Table 6.1 summarises the ACTION values and transaction types.