Stuff

    $menue_eintraege = $db->getRows("
    SELECT  `id` `title`
    FROM `system_menue`
    WHERE `kategorie` = ?
    ORDER BY `id` ASC;
    ", $_POST['kat']);

    foreach($menue_eintraege as $menue_eintrag){
        echo $menue_eintrag['id'];
    }