Change user name after authentication

If you implemented a custom authentication backend and want to change the username provide by the user after authentication, e.g. you want to allow login via a unique id that could change sometime (e.g. email address), but use another unmodifiable unique id as permanent identifier in Dokuwiki. Then implement your checkPass function with the $user parameter passed by reference:

function checkPass(&$user,$pass)
    $user = $some_unique_id_fetched_from_your_own_user_db; // you can now change the user and it will be changed in the calling scope as well
    return true;
    return false;