Handling JSON in PHP

After reading this Book, you will be able to understand, work and test JSON code with PHP.
There are already lots of tutorials out there on handling JSON with PHP, but most of them don't go much deeper than throwing an array against json_encode and hoping for the best. This article aims to be a solid introduction into JSON and how to handle it correctly in combination with PHP. Also, readers who don't use PHP as their programming language can benefit from the first part that acts as a general overview on JSON.
JSON (JavaScript Object Notation) is a data exchange format that is both lightweight and human-readable (like XML, but without the bunch of markup around your actual payload). Its syntax is a subset of the JavaScript language that was standardized in 1999. If you want to find out more, visit the official website.
The cool thing about JSON is that you can handle it natively in JavaScript, so it acts as the perfect glue between server- and client-side application logic. Also, since the syntactical overhead (compared to XML) is very low, you need to transfer less bytes of ther wire. In modern web stacks, JSON has pretty much replaced XML as the de-factor payload format (aside from the Java world I suppose) and client side application frameworks like backbone.js make heavy use of it inside the model layer.
Before we start handling JSON in PHP, we need to take a short look at the JSON specification to understand how it is implemented and what's possible.