By August 15, 2009, all calls to the Amazon® Product Advertising API must be signed to authenticate the request. Ulrich Mierendorff developped a simple function in PHP that lets you make authenticated requests with only a few lines of code. He is also the author of “Antialiased filled Arcs/Ellipses” for PHP and of the rounded css boxes.

Other PHP example for Amazon signed requests have been posted by Mark on his blog “Every Good Path” and by Horacix on his blog “Inside Things“.

Amazon’s guidelines for signing requests are available on the AWS website.

The following error messages are sent:

• the timestamp is old : Request has expired