【裝飾模式】遵循開閉原則，使用一個類裝飾另一個類

這個設計模式，說真的，我還沒讀懂，讀懂的兄弟可以留言幫我解釋一下，我需要 慢慢的研究 這 中模式的好處，和優點，先附上我的代碼

abstract class component{
    abstract public function operation();
}

class concreteComponent extends component {
    public function operation()
    {
        // TODO: Implement operation() method.
        echo '這裡是具體操作';
    }
}

abstract class Decoratr extends component {
    protected $component;
    public function setComponent($component){
        $this->component = $component;
    }
    public function operation()
    {
        // TODO: Implement operation() method.
        if($this->component!=null){
            $this->component->operation();
        }
    }
}

class A extends Decoratr {
    private $state;

    public function operation()
    {
        parent::operation(); // TODO: Change the autogenerated stub
        $this->state = 'new state';
        echo '裝飾A';
    }
}

class B extends Decoratr {
    public function operation()
    {
        parent::operation(); // TODO: Change the autogenerated stub
        $this->behavior();
        echo '裝飾B';
    }
    public function behavior(){

    }
}

$c = new concreteComponent();
$a = new A();
$b = new B();

$a->setComponent($c);
$b->setComponent($a);
$b->operation();

看完之後，我凌亂了