/**   * Subject interface.   * Client depends only on this abstraction.   */ interface Image  {      public function getWidth();      public function getHeight();      public function getPath();      /**       * @return string   the image's byte stream       */     public function dump();  }  /**   * Abstract class to avoid repetition of boilerplate code in the Proxy   * and in the Subject. Only the methods which can be provided without   * instancing the RealSubject are present here.   */ abstract class AbstractImage implements Image  {      protected $_width;      protected $_height;      protected $_path;      protected $_data;      public function getWidth()      {   return $this->_width;      }      public function getHeight()      {   return $this->_height;      }      public function getPath()      {   return $this->_path;      }  }  /**   * The RealSubject. Always loads the image, even if no dump of the data   * is required.   */ class RawImage extends AbstractImage  {      public function __construct($path)      {   $this->_path = $path;   list ($this->_width, $this->_height) = getimagesize($path);   $this->_data = file_get_contents($path);      }      public function dump()      {   return $this->_data;      }  }  /**   * Proxy. Defers loading the image data until it becomes really mandatory.   * This class does its best to postpone the very expensive operations   * such as the actual loading of the BLOB.   */ class ImageProxy extends AbstractImage  {      public function __construct($path)      {   $this->_path = $path;   list ($this->_width, $this->_height) = getimagesize($path);      }      /**       * Creates a RawImage and exploits its functionalities.       */     protected function _lazyLoad()      {   if ($this->_realImage === null) {       $this->_realImage = new RawImage($this->_path);   }      }      public function dump()      {   $this->_lazyLoad();   return $this->_realImage->dump();      }  }  /**   * Client class that does not use the data dump of the image.   * Passing blindly a Proxy to this class and to other Clients makes sense   * as the data would be loaded anyway when Image::dump() is called.   */ class Client  {      public function tag(Image $img)      {   return ';      }  }  $path = '/home/giorgio/shared/Immagini/kiki.png';  $client = new Client();  $image = new RawImage($path); // loading of the BLOB takes place  echo $client->tag($image), "\n";  $proxy = new ImageProxy($path);  echo $client->tag($proxy), "\n"; // loading does not take place even here