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：

//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Aclass 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Bclass 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() { $decoratorA = new ConcreteDecoratorA(new ConcreteComponent()); $decoratorA->operation(); $decoratorB = new ConcreteDecoratorB($decoratorA); $decoratorB->operation(); } } Client::main();