Sameer Borate recently posted this new look at hooking your PHP application into the Amazon Product Advertising API to use the updated key system Amazon has put in place.
In this post we will see how to access the Amazon Product Advertising API from PHP. Amazon has recently changed (from 15th Aug '09) the authentication mechanism for accessing their API which must now be signed with your Amazon keys. Unsigned requests will be rejected by Amazon. Note that the code uses the hash_hmac() hash function which is only available for PHP versions 5.1.2 and above, so the code will not work for versions below that.
The full code, including an example if it in action - connecting to the API and searching for the DVD of "X-Men Origins". The full code of his class is included, perfect for cut and pasting.