Magic methods for properties ( php )

<?php

 class Car
 {

 	public $manufacturer;
 	public $model;
 	public $color;
 	private $_extraData = array();

 	/**
 	 * __get() gets called when code try to read invisible property
 	 * @param unknown $propertyName
 	 * @return multitype:|NULL
 	 */
 	public function __get( $propertyName )
 	{
 		if( array_key_exists( $propertyName , $this->_extraData) )
 		{
 			return $this->_extraData[$propertyName];
 		}

 		else
 		{
 			return null;
 		}
 	}

 	/**
 	 * __set() gets called when code try to write invsible property of the object
 	 * @param unknown $propertyName
 	 * @param unknown $propertyValue
 	 */
 	public function __set( $propertyName , $propertyValue  )
 	{
 		$this->_extraData[$propertyName] = $propertyValue;

 		echo "<pre>";
 		print_r($this->_extraData);
 		echo "</pre>";
 	}

 }

   $myCar = new Car();
   $myCar->manufacturer = "Volkswagen";
   $myCar->model = "Beetle";
   $myCar->color = "red";

   $myCar->engineSize = 1.8;
   $myCar->otherColors = array( "green" , "blue" , "purple" );

//    var_dump( $myCar->otherColors );

   var_dump( property_exists( "Car"  , 'engineSize' ) );
   var_dump( property_exists( "Car"  , 'color' ) );


?>