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();
原文：http://www.jb51.net/article/65841.htm