一個很不錯的抽象類的實現

<?php
/*
 * Created on 2011-5-16
 *
 * To change the template for this generated file go to
 * Window - Preferences - PHPeclipse - PHP - Code Templates
 */
abstract class car{

    abstract function getMaxSpeed();
}

class FastCar extends car{

    function getMaxSpeed()
    {
        return 500;
    }


}


class SlowCar extends car{

    function getMaxSpeed()
    {
        return 50;
    }

}



class Street{

    protected $speedLimit;
    protected $cars;
    public function __construct($speedLimit=200)
    {
        $this->cars=array();
        $this->speedLimit=$speedLimit;
    }

    protected function islegal($car)
    {
        if($car->getMaxSpeed() < $this->speedLimit)
            return true;
        else
            return false;

    }

    public function addcars($car)
    {
        if($this->islegal($car))
        {
            echo "this car is allowed to run in the street";
            $this->cars[]=$car;
        }else{
            echo "it's fobidden to run";

        }


    }


    public function getcarslist()
    {
        print_r($this->cars);
    }

}

$b=new street();
$b->addcars(new FastCar);
echo "<br>";
$b->addcars(new SlowCar);
$b->addcars(new SlowCar);
$b->addcars(new SlowCar);
$b->addcars(new SlowCar);
$b->addcars(new SlowCar);

$b->getcarslist();
?>