Ajax order update on Prestashop, php part

AdminOrdersController.php

//I know, it's horrible

		if ($_POST['action']=='ajaxOrderUpdate'){
	 		
	 		$orderId = $_POST['order_id'];
	 		$changeTo = $_POST['change_to'];
	 					
			Db::getInstance()->update('order_carrier', array(
			    'tracking_number'  	=> $changeTo,
			),
			'id_order =' . $orderId, 1
			);

			//$sql = new DBQuery();
			//$sql->select('tracking_number');
			//$sql->from('order_carrier');
			//$sql->where('id_order =' . $orderId);
			//$dbResponse = Db::getInstance()->executeS($sql);

	 		die();
		}