Dependency Injection With default configuration demo

index.php

<?php
/**
* inspired on a series of articles from @fabpot
* url: http://fabien.potencier.org/article/11/what-is-dependency-injection
* 
* These examples are made by @stefanooldeman and its purpose is to demo the idea and 
* tooling of DI and make it clear in very short 'real world' example without pointing to any framework. 
* btw: i did not see symfony's sfServiceContainer DI helpe module (yet) but i get the idea ;)
*/


//todo: autoload or include ServiceContainer and User class

//This could be any class. but for now a simple one
class MyCacheHelper {
	private $config;

	public function __construct($config) {
		$this->config = $config;
	}
}

//configure the defeault dependency object
$service = new ServiceContainer(array('cache' => 'MyCacheHelper'));

$user = new User();
var_dump($user->getCache());

ServiceContainer.php

<?php
class ServiceContainer implements ArrayAccess {

	static protected $instance;

	public $parameters = array();

	public function __construct(array $parameters = array()) {
		$this->parameters = $parameters;

		if(self::$instance == null) {
			self::$instance = $this;
		}
	}

	//implement interface
	public function offsetSet($offset, $value) {
		self::$instance->parameters[$offset] = $value;
	}

	public function offsetExists($offset) {
		return isset(self::$instance->parameters[$offset]);
	}

	public function offsetUnset($offset) {
		unset(self::$instance->parameters[$offset]);
	}

	public function offsetGet($offset) {
		return isset(self::$instance->parameters[$offset]) ? self::$instance->parameters[$offset] : null;
	}

}

User.php

<?php
class User extends ServiceContainer {

	static protected $shared = null;

	protected function getCacheConfig() {
		return array(
			'lifetime' => (7 * 24 * 60 * 60)
			//whatever else you need
		);
	}

	public function getCache() {
		if(!isset(self::$shared)) {
			$class = new $this['cache']($this->getCacheConfig());
			self::$shared = $class;
		}

		return self::$shared;
	}

}