定义：

装饰者模式就是不修改原类代码和继承的情况下动态扩展类的功能。传统的编程模式都是子类继承父类实现方法重载，使用装饰器模式，只需添加一个新的装饰器对象，更加灵活，避免类数量和层次过多。

角色：

Component（被装饰对象基类） ConcreteComponent（具体被装饰对象） Decorator（装饰者基类） ContreteDecorator（具体的装饰者类）

示例代码：

<div class="jb51code">
<pre class="brush:php;">
//被装饰者基类
interface Component
{
public function operation();
}

//装饰者基类
abstract class Decorator implements Component
{
protected $component;

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

public function operation()
{
$this->component->operation();
}
}

//具体装饰者类
class ConcreteComponent implements Component
{
public function operation()
{
echo 'do operation'.PHP_EOL;
}
}

//具体装饰类A
class ConcreteDecoratorA extends Decorator {
public function construct(Component $component) {
parent::construct($component);

}

public function operation() {
parent::operation();
$this->addedOperationA(); // 新增加的操作
}

public function addedOperationA() {
echo 'Add Operation A '.PHP_EOL;
}
}

//具体装饰类B
class ConcreteDecoratorB extends Decorator {
public function construct(Component $component) {
parent::construct($component);

}

public function operation() {
parent::operation();
$this->addedOperationB();
}

public function addedOperationB() {
echo 'Add Operation B '.PHP_EOL;
}
}

class Client {

public static function main() {
/
do operation
Add Operation A
/
$decoratorA = new ConcreteDecoratorA(new ConcreteComponent());
$decoratorA->operation();

/*
do operation
Add Operation A 
Add Operation B 
*/
$decoratorB = new ConcreteDecoratorB($decoratorA);
$decoratorB->operation();

}

}

Client::main();