public function loginAction()
    {
        if(isset($_POST['username']) && isset($_POST['psw'])
        && isset($_POST['submit']))
        {
            $arr = [];
            $username = htmlentities($_POST['username']);
            $password = htmlentities($_POST['psw']);
            $manager = new UserManager();
            $getUserData = $manager->loginUser($username, $password);
            $arr['user'] = $_SESSION['username'];
            var_dump($arr);
        }
        return $this->render('login.html.twig', $arr);
    }

public function loginUser($user, $password)
    {
        if(isset($user) && isset($password)
        && isset($_POST['submit']))
        {
            $hashedPwd = hash(md5, $password);
            $dbm = DBManager::getInstance();
            $pdo = $dbm->getPdo();

            $stmt = $pdo->prepare("SELECT * FROM `Users`(`username`, `password`)
            VALUES (:username, :pwd)");
            $stmt->bindParam(':username', $user);
            $stmt->bindParam(':pwd', $hashedPwd);

            $stmt->execute();
            $result = $stmt->fetchAll();

            return $result;
        }
    }

<form action="?action=login" method="POST">
    <input type="text" placeholder="username" name="username"><br>
    <input type="password" placeholder="password" name="psw"><br>
    <button type="submit" name="submit">Login boi</button>
</form>

<p>Hello {{ user }}</p>

protected function render($view, $data = [])
    {
        global $twig;
        $template = $twig->load($view);
        $response = $template->render($data);

        return $response;
    }