Programming PHP, 4th Edition

Chapter 13. JSON

Similar to XML, JavaScript Object Notation (JSON) was designed as a standardized data-interchange format. However, unlike XML, JSON is extremely lightweight and human-readable. While it takes many syntax cues from JavaScript, JSON is designed to be language-independent.

JSON is built on two structures: collections of name/value pairs called objects (equivalent to PHP’s associative arrays) and ordered lists of values called arrays (equivalent to PHP’s indexed arrays). Each value can be one of a number of types: an object, an array, a string, a number, the Boolean values TRUE or FALSE, or NULL (indicating a lack of a value).

Using JSON

The json extension, included by default in PHP installations, natively supports converting data to JSON format from PHP variables and vice versa.

To get a JSON representation of a PHP variable, use json_encode():

$data = array(1, 2, "three");
$jsonData = json_encode($data);
echo $jsonData;
[1, 2, "three"]

Similarly, if you have a string containing JSON data, you can turn it into a PHP variable using json_decode():

$jsonData = "[1, 2, [3, 4], \"five\"]";
$data = json_decode($jsonData);
print_r($data);
Array( [0] => 1 [1] => 2 [2] => Array( [0] => 3 [1] => 4 ) [3] => five)

If the string is invalid JSON, or if the string is not encoded in UTF-8 format, a single NULL value is returned instead.

The value types in JSON are converted to PHP equivalents as follows:

object

An associative array containing the object’s key-value pairs. Each ...