Евгений Куманин

В объектно-ориентированном программировании есть очень много полезных вещей.
Например наследование.

// describe interfate of engine
interface IEngine {
  public function getAcceleration();
  public function getPower();
}

// abstract implementation of engine
abstract class Engine implements IEngine {

  /**
   * Engine acceleration
   */
  protected $_acceleration = 0;

  /**
   * Engine power (h/p)
   */
  protected $_power = 0; 

  public function getAcceleration() {
    return (int) $this->_acceleration;
  }

  public function getPower() {
    return (int) $this->_power;
  }
}

// extending from engine implementation
class V12 extends Engine{
  protected $_acceleration = 0.0005;
  protected $_power = 300; 
}

// describe interface of the car
interface ICar {
  public function setEngine(IEngine $engine);
  public function accelerate();
}

// abstract implementation of engine
abstract class Car {

  /**
  * Engine of the car
  * @var IEngine
  */
 protected $_engine;

 /**
  * Speed of the car
  * @var Float
  */
 protected $_speed = 0;

 public function setEngine(IEngine $engine){
  $this->_engine = $engine;
 }

 public function accelerate() {
  if( ! ($this->_engine instanceof IEngine)){
    throw new Exception("Wrong type of engine");
  }

  $this->_speed += $this->_engine->getAcceleration();
 }
} 

class MyCar extends Car {
 public function __construct(){
   $this->setEngine(new V12());
 }
}

$car = new MyCar();
$car->accelerate();