protected function fillRowExcel($a_worksheet, &$a_row, $a_set)
{
$a_worksheet->write($a_row, 0, $a_set["login"]);
$a_worksheet->write($a_row, 1, $a_set["firstname"]);
$a_worksheet->write($a_row, 2, $a_set["lastname"]);
$a_worksheet->write($a_row, 3, ilFormat::_secondsToShortString($a_set["online_time"]));
$a_worksheet->write($a_row, 4, ilDatePresentation::formatDate(new ilDateTime($a_set["last_login"], IL_CAL_DATETIME)));
}