Updated: 19th October 2011
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. Also now Amazon Associate Tag is required in the query (effective from 25th Oct. 2011). 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.