In php how to determine the event number - by: Russell Noble

Hi,
I'm wondering across the frontend and backend is there a consistent way of determining the current event id being processed?
For example, in a field $this->eventId seems to work, but not always. Sometimes $eventId = JRequest::getInt('event_id', 0); works.

In registrant management at the front end I cant seem to find a variable with the event id, $this->eventId is not set within the field php, but at the backend it is set.

Thanks,
Russell