Cart API encoding and decoding engine for PHP. Used by cart plugins implementing the Cart API protocol. If you are developing a new cart plugin in a PHP-based environment, use the PHP classes provided here to encode and decode the various Cart API protocol entities.

• CartAPI_Engine - The general engine class, use this class when handling a Cart API request. Contains utility functions that handle a new request, parse the request metadata and initialize the correct encoder/decoder classes according to the metadata. For handling a new Cart API request, all you have to do is use the function CartAPI_Engine::handleRequest() which parses all the relevant arguments and initializes the correct encoder.
• CartAPI_Helpers - Class containing various static helper utility functions. For example, use CartAPI_Helpers::createSuccessResponse() to create a successful response to the Cart API request, or use CartAPI_Helpers::dieOnError() to create a failure response and exit.

Cart API supports various mediums for encoding/decoding protocol calls. For example, XML over HTTP POST and JSON over HTTP GET are two different mediums. For more information about mediums see Cart API mediums reference.

• XML - Implementation of encoder/decoder for the XML over HTTP POST medium.
• JSON - Implementation of encoder/decoder for the the JSONP over HTTP GET medium.

• CartAPI_Mediums_Encoder - Base class for an encoder. All encoders (for the various supported mediums) inherit from it. Should not be used directly.