public function login($userName, $password){
            $this->connection = Database::getInstance()->OpenConnection();
            $sql = "select * from user where user_name = ? and password = ?;";

            $statement = mysqli_prepare($this->connection, $sql);

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

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

            echo "teste: ".$user->name;

            //close statement and connection
            $statement->close();
            Database::getInstance()->CloseConnection($this->connection);

            return $user;
        }