How to use PHP factory mode_PHP tutorial

class MyObject{
//The object will be returned from the factory
}
class MyFactory{
public static function factory(){
return new MyObject():
}
}
$instance=MyFactory::factory();

interface IImage{
function getHeight();
function getWidth();
function getData();
}
class Image_PNG implements IImage{
private $_width,$ _height,$_data;
public function __construct($file){
$this->_file=$file;
$this->_parse();
}
private function _parse(){
//Complete the parsing of PNG format
//Fill in $_width, $_height, $_data;
}
public function getWidth(){
return $this ->_width;
}
public function getHeight(){
return $this->_height;
}
public function getData(){
return $this-> ;_data;
}
}
class Image_JPEG implements IImage{
private $_width,$_height,$_data;
public function __construct($file){
$this-> ;_file=$file;
$this->_parse();
}
private function _parse(){
//Complete the parsing of JPEG format
//And fill in $ _width,$_height,$_data;
}
public function getWidth(){
return $this->_width;
}
public function getHeight(){
return $ this->_height;
}
public function getData(){
return $this->_data;
}
}
class ImageFactory{
public static function factory($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:
// There is a problem
}
if($ret instanceof IImage){
return $ret;
}else {
//There is a problem
}
}
}
//When calling the factory method using the image file name, different objects are obtained depending on the file type passed in.
//Call ImageFactoyr
$image=ImageFactory::factory('/path/to/my.jpg');
//$image is an instance of the Image_JPEG class
echo $image- >getWidth();

interface IDatabaseBindings{
public function userExists($email);
}
class PGSQL implements IDatabaseBindings{
protected $_connection;
public function __construct(){
$this->_connection=pg_connect('dbname=example_db');
}
public function userExists($email){
$emailEscaped=pg_escape_string ($email);
$query="select 1 from users where email='".$emailEscaped."'";
if($result=pg_query($query,$this->_connection)) {
return (pg_num_rows($result)>0)?true:false;
}else{
return false;
}
}
}
class MYSQL implements IDatabaseBindings{
protected $_connection;
public function __construct(){
$this->_connection=mysql_connect('localhost');
mysql_select_db('example_db',$this->_connection );
}
public function userExists($email){
$emailEscaped=mysql_real_escape_string($email);
$query="select 1 from users where email='".$emailEscaped." '";
if($result=mysql_query($query,$this->_connection)){
return (mysql_num_rows($result)>0)?true:false;
}else{
return false;
}
}
}
class DatabaseFactory{
public static function factory(){
$type=loadtypefromconfigfile();
switch ($ type){
case 'PGSQL':
return new PGSQL();
break;
case 'MYSQL':
return new MYSQL();
break;
}
}
}

//Call DatabaseFactoy
$db=DatabaseFactory::factory();
$db->userExists('person@example.com');