interface

interface ISpeedInfo
{
    function getMaximumSpeed();
}

class Car{
   
}

class FastCar extends Car implements ISpeedInfo
{
    function getMaximumSpeed()
    {
        return 150;
    }
}

class Street
{
    protected $speedLimit;
    protected $cars;
   
    public function __construct($speedLimit = 200)
    {
        $this->cars = array();
        $this->speedLimit = $speedLimit;
    }
   
    protected function isStreetLegal($car)
    {
        if($car instanceof ISpeedInfo){
            if($car->getMaximumspeed()<$this->speedLimit)
            {
                return ture;
            } else {

                 //扩展类必须实现ISpeedInfo才能使Street合法
                return false;
            }
        return false;
        }
    }
   
    public function addCar($car)
    {
        if($this->isStreetLegal($car))
        {
            echo 'The Car was allowed on the road.';
            $this->cars[] = $car;
        } else {
            echo 'The Car is too fast and was not allowed on the road.';
        }
    }
   

}

    $street = new Street();
    $street->addCar(new FastCar());
?>

输出 The Car was allowed on the road.

 

intanceof:返回一个BOOLEAN类型的值。用来确定对象的某个实例是否为特定的类型，或者是否从某个类型继承，又或者是否实现了某个特定的接口。