Dependency_injection

Dependency Injection is a process by which the components a class uses are supplied to it by a container instead of the class itself locating them. This allows a ton of flexibility for testing, special cases, and polymorhpism, and it follows the "tell, don't ask" software design principle.

The Xyster team has implemented a PHP Dependency Injection container. Here's an example of how you might use the container. (This example is adapted into PHP from one listed on the PicoContainer site).

interface Peelable {  
    function peel();  
}  
class Apple implements Peelable {  
    public function peel()
    {  
    }  
}
class Peeler {  
    private $_peelable;  
    public function __construct(Peelable $peelable)
    {  
        $this->_peelable = $peelable;  
    }  
}
class Juicer {  
    private $_peelable;  
    private $_peeler;  
    public function __construct(Peelable $peelable, Peeler $peeler)
    {  
        $this->_peelable = $peelable;  
        $this->_peeler = $peeler;  
    }  
}

Add components:

$container = new Xyster_Container;
$container->autowire("Apple");
$container->autowire("Juicer");
$container->autowire("Peeler");

Get component with dependencies injected:

$juicer = $container->get("Juicer");

If you're curious about the implementation and would like to test it out before it's stable, have a look at Xyster\Container.