$connection = Database::getInstance()->OpenConnection();
            $sql = "select * from user where user_name = ? and password = ?;";
            $statement = $connection->prepare($sql);

            //if any error happen in connection
            if (!$statement) {
                echo 'erro na consulta: '. $connection->errno .' - '. $connection->error;
            }

            //associate the user name and password with sql parameters,
            //execute the query and store the result
            $statement->bind_param('ss', $user,$password);
            $statement->execute();
            $result = $statement->get_result();

            $user;
            //create and set the user variable
            while($row = mysqli_fetch_array($result)){
                $user = new User($row["idUser"], $row["name"], $row["email"], $row["user_name"], $row["password"], $row["type"], $row["active"], $row["idAdministrator"]);
            }