gistfile1.php

class Cars
{
  function createCar($brand)
  {
    $car_obj = 0;
    switch ($brand) {
      case 'toyota': $car_obj = new Toyota;
      case 'bmw':    $car_obj = new Bmw;
      default:       $car_obj = new Toyota;
    } 
    return $car_obj;
  }
}

abstract class Car
{
  abstract function getMaxSpeed();
  abstract function getWeight();
}

class Toyota extends Car
{
  public function getMaxSpeed() {
  }
}