function referenten_sort(Referent $a, Referent $b)
{
$cmp_days = $a->getVortrag()->day - $b->getVortrag()->day;
if ($cmp_days == 0) {
$cmp_slots = $a->getVortrag()->slot - $b->getVortrag()->slot;
if ($cmp_slots == 0) {
$cmp_titles = strcmp($a->getVortrag()->title, $b->getVortrag()->title);
if ($cmp_titles == 0) {
return strcmp($a->name, $b->name);
} else {
return $cmp_titles;
}
} else {
return $cmp_slots;
}
} else {
return $cmp_days;
}
}
