PHP设计模式---工厂模式

interface IImage{
function getHeight();
function getWidth();
function getData();
}
//png图片
class Image_PNG implements IImage{
private $_width,$_height,$_data;
public function __construct($file){
$this->_file=$file;
$this->_parse();
}
private function _parse(){
//
echo 'You are a png img!';
}
function getHeight(){
return $this->_height;
}
function getWidth(){
return $this->_width;
}
function getData(){
return $this->_data;
}
}
//jpeg
class Image_JPEG implements IImage{
private $_width,$_height,$_data,$_file;
public function __construct($file){
$this->_file=$file;
$this->_parse();
}
private function _parse(){
//*************
$img=Image::getImageInfo($this->_file);
$this->_width=$img[0];
echo 'You are a jpeg image o!';
}
function getHeight(){
return $this->_height;
}
function getWidth(){
return $this->_width;
}
function getData(){
return $this->_data;
}
}
//图片格式工厂
class ImageFactory{
public static function factory($file){
$pathParts=pathinfo($file);
switch (strtolower($pathParts['extension'])){
case 'jpg':
$ret=new Image_JPEG($file);
break;
case 'png':
$ret=new Image_PNG($file);
break;
default:// 有问题
}
if ($ret instanceof  IImage){
return $ret;
}else {
//有问题
}
}
}
//调用
$image=ImageFactory::factory("D:\\My Documents\\My Pictures\\aa.jpg");
echo $image->getWidth();