_bulb = $bulb;    }    public function execute() {        $this->_bulb->turnOn();    }    public function undo() {        $this->_bulb->turnOff();    }    public function redo() {        $this->_bulb->turnOn();    }}class TurnOff implements Order {    private $_bulb;    public function __construct($bulb) {        $this->_bulb = $bulb;    }    public function execute() {        $this->_bulb->turnOff();    }    public function undo() {        $this->_bulb->turnOn();    }    public function redo() {        $this->_bulb->turnOff();    }}class Control {    public function submit($order) {        $order->execute();    }}$bulb = new Bulb();$turnOn = new TurnOn($bulb);$turnOff = new TurnOff($bulb);$control = new Control();$control->submit($turnOn);echo PHP_EOL;$control->submit($turnOff);