三个类概括PHP的五种设计模式

class people {
    private $name = '';
    private $user = null;

    private function __constract($name){/*此处private定义辅助实现 单元素模式*/
        $this->name = $name;
    }

    public static function instance($name){/*此方法实现 工厂模式*/
        static $object = null;/*此变量实现 单元素模式*/
        if (is_null($object))
            $object = new people($name);
        return $object;
    }

    public function work_in($who=null)
    {
        if (is_null($who)) echo 'error';
        else {
            $this->user[] = $who;/*此数组变量实现 观察者模式*/
            echo $who->work();/*此方法调用实现 策略模式*/
        }
    }

    public function on_action($which=''){
        if (empty($which)) echo 'error';
        else {
            foreach ($this->user as $user)
                $user->action($which);/*此方法调用实现 命令链模式*/
        }
    }
}

$people = people::instance('jack');
$people->work_in(new student);
$people->work_in(new teacher);
$people->on_action('eat');

class student {
    function work(){
        echo '<br/>我是学生，朝九晚五。';
    }

    function action($which){
        if (method_exists($this, $which)) return $this->$which();
        else echo 'you are wrong!';
    }

    function eat(){
        echo '<br/>我是学生，只能吃套餐。';
    }
}

class teacher {
    function work(){
        echo '<br/>我是老师，晚上备课最忙。';
    }

    function action($which){
        if (method_exists($this, $which)) return $this->$which();
        else echo 'i can not do it!';
    }

    function eat(){
        echo '<br/>我是老师，可以每天吃大餐。';
    }
}