/**
* 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