function login()
{
    $request = Slim::getInstance()->request();
    $user = json_decode($request->getBody());
    $dao = new \DAO\UserDAO();
    session_start();
    if ($dao->validateUser($user->username, $user->password)) {
        $u = $dao->getUserById($user->username);
        $_SESSION["loggedIn"] = true;
        $_SESSION["username"] = $u->getUsername();
        $_SESSION["role"] = $u->getRole();
    } else {
        session_destroy();
    }
}