Encode/Decode POST data in php

Encode/Decode POST data in php

I'm using cURL to play around with POSTing and retrieving pages. I'm
noticing that the site I'm trying to POST data to encodes it, for example:
Data=%7B%22Data%22%3A%22%5B%7B%5C%22
How can I encode/decode this in PHP? I've found web sites that do it for
me but I would like to learn how to do it myself.