装饰模式

/**
* 规定装饰类与被装饰类都必须实现的方法
*/
interface component {
function operation();
}
/**
* 被装饰的类
*/
class concrete_component implements component {
public function operation() {
echo '具体履行职责的对象<br/>';
}
}

/**
* 装饰器抽象类
*/
abstract class decorator_component implements component {
protected $component;
/**
* 添加装饰器方法
*/
public function set_component (component $component) {
$this->component = $component;
}
public function operation() {
if( $this->component != null ) {
$this->component->operation();
}
}
}

/**
* 第一个装饰器
*/
class decorator_a extends decorator_component{
public function operation() {
parent::operation();
echo 'decorator_a<br/>';
}
}

/**
* 第二个装饰器
*/
class decorator_b extends decorator_component{
public function operation() {
parent::operation();
echo 'decorator_b<br/>';
}
}

$concrete_component = new concrete_component();

$decorator_a = new decorator_a();
$decorator_a->set_component($concrete_component);

$decorator_b = new decorator_b();
$decorator_b->set_component($decorator_a);
$decorator_b->operation();