Finish Dasar Pemograman Berorientasi Objek (PBO) di PHP

<?php
class handphone {
 public $kamera;
 public $tahun;
 public $layar_sentuh = true;
  public function __construct($kamera, $tahun){
    $this->kamera = $kamera;
    $this->tahun = $tahun;
  }
  public function ambil_photo(){
    return "$this->kamera jepret...!!";
  }
}
$canggih = new handphone("kamera : 8 Megapixels", "tahun : 2013");
$jadul = new handphone("kamera : 2 Megapixels", "tahun : 2012");
$jadul->layar_sentuh = false;
echo $canggih->ambil_photo();
?>