public function applies($site_id, $is_child, $theatre_id, $subspecialty_id, $firm_id)
{
foreach (array('site_id', 'is_child', 'theatre_id', 'subspecialty_id', 'firm_id') as $field) {
if ($this->{$field} !== null && $this->{$field} != ${$field}) {
return false;
}
}
return true;
}