PHP (单例模式与工厂模式)

/*
 * 
 * 单例模式
 * 
 */
class DB {

    private $conn;
    static private $_instance;
    
    function __construct() {
        $this->conn = mysql_connect('xxxxx');
    }
    function getInstance(){
        if(!(self::$_instance instanceof self)){
            self::$_instance = new self();
        }
        return self::$_instance;
    }
    
    function adduser(){
        
    }
}
//$db = DB::getInstance();
//$db->adduser;


/**
 * 工厂模式
 * 
 */

//产品类
abstract class BMW{
    function __construct() {
        echo 'this is BMW car ';
    }

}
class BMW320 extends BMW{
    function __construct(){
        echo parent::__construct();
        echo 'this is BMW320';
    }
}
class BMW750 extends BMW{
    function __construct(){
        echo parent::__construct();
        echo 'this is BMW750';
    }   
}


//工厂类
interface Factory{
       function createCar(); 
}

class createBMW320 implements Factory{
    function createCar() {
        return new BMW320();
    }
}
class createBMW750 implements Factory{
    function createCar() {
        return new BMW750();
    } 
}

       
//客户类
$mycar = new createBMW750();
$car =$mycar->createCar();
var_dump($car);