Yaf中init方法一開始就實例化多個類別並把它們存在私有屬性中與需要再去new 類別有什麼區別嗎？

<code>class Order{
    private $extend     = '';
    private $order      = '';
    public function init(){
        parent::init();
        $this->order      = new Order();
        $this->extend     = new OrderEx();
    }

    public function listAction(){
        $this->order->public();
    }
    
    public function makeAction(){
        $this->extend->public();
    }
}</code>

<code>class Order{
    private $extend     = '';
    private $order      = '';
    public function init(){
        parent::init();
    }

    public function listAction(){
        $order = new Order();
        $order->public();
    }
    
    public function makeAction(){
        $extend= new extend();
        $extend->public();
    }
}</code>