Compatible version of PHP 5.4's JsonSerializable

use.jsonSerializable.php

<?php
if (!interface_exists('JsonSerializable')) {
	define('IJsonSerializable', false);
	
	// inline interface.JsonSerializable.php
	interface JsonSerializable {
		public function jsonSerialize();
	}
} else {
	define('IJsonSerializable', true);
}

class ArrayValue implements JsonSerializable {
	public function __construct(array $array) {
		$this->array = $array;
		$this->otherArray = $array;
	}

	public function jsonSerialize() {
		return $this->array;
	}
}

$array = array(1, 2, 3);
$obj = new ArrayValue($array);

if (!IJsonSerializable) {
	echo json_encode($obj->jsonSerialize()).PHP_EOL;
} else {
	echo json_encode($obj).PHP_EOL;
}
?>