How to add the URL encoded signature to your request
Amazon changed the way they authenticate user who use Product Advertising API. In the REST call, you must have Signature parameter in order to request for a service. Below is the functions that helps you encode the request URL in order to add to your request before calling Amazon API for product search and details. Make sure your server support mHash functionality. On Windows, you can enable mhas.dll extension in your php.ini file. On Linux, you can follow this instruction