interface FlyWeight

{

    public function __construct($uid);

}

class User implements FlyWeight

{

    protected $uid;

    public function __construct($uid)

    {

        $this->uid = $uid;

    }

    public function __toString()

    {

        return 'uid' . $this->uid . PHP_EOL;

    }

}

class Factory

{

    public static $users = array();

    public static function getUser($uid)

    {

        if (! array_key_exists($uid, self::$users)) {

            self::$users[$uid] = new User($uid);

        }

        return self::$users[$uid];

    }

}

$user1 = Factory::getUser(1);

$user2 = Factory::getUser(2);

$user3 = new User(3);

echo($user1);

echo($user2);

echo($user3);