<?php
//定义接口
interface FlyBehavior{
    public function fly();
}
 //具体方法实现（例子中有不同的飞行方式）
class FlyWithWings implements FlyBehavior{
    public function fly(){
        echo "Fly With Wings \n";
    }
}

class FlyWithNo implements FlyBehavior{
    public function fly(){
        echo "Fly With No Wings \n";
    }
}
//定义鸭子的超类
class Duck{
    private $_flyBehavior;
    public function performFly(){
        $this->_flyBehavior->fly();
    }

    public function setFlyBehavior(FlyBehavior $behavior){
        $this->_flyBehavior = $behavior;
    }
}
//继承超类
class RubberDuck extends Duck{
}
// Test Case
$duck = new RubberDuck();

/*  想让鸭子用翅膀飞行 */
$duck->setFlyBehavior(new FlyWithWings());
$duck->performFly();            

/*  想让鸭子不用翅膀飞行 */
$duck->setFlyBehavior(new FlyWithNo());
$duck->performFly();