';    }    function sleep()    {        echo '猫正在睡觉！
';    }}class Dog implements Doing{    function eat()    {        echo '狗正在吃东西！
';    }    function sleep()    {        echo '狗正在睡觉！
';    }}class Factory{    static function createDoing(){}}class CatFactory implements Factory{    static function createDoing()    {        return new Cat();    }}class DogFactory implements Factory{    static function createDoing()    {        return new Dog();    }}