php json_encode and json_decode
JSON is used in many places on the web. It got it's start with ajax and has trickled into use in many other places. It is being used a lot now with web API's and I have even seen it make it's way into being used as a simple way to store serialized objects.
PHP has recognized the importance of JSON in today's web, with later versions of php the json_encode and json_decode functions are included in the core build. In versions earlier than 5.2 you may need to install the extension for these functions.