CiviEvent: possible to trigger an email to event organizer when participant count reaches a certain number?

Question

I'd like to be able to notify organizers when a certain number of participants have registered. I don't want to shut down registration or offer a waiting list to participants, I just need the staff notified via email.

Is there a way to do this out-of-the-box? Could I do this with the CiviRules component? If not, other suggestions on hooks/customizations welcome.

Thanks!

System deets: Joomla 3.8.12, CiviCRM 5.3.1

Answer 1

It can be easily done using hooks. Max participant is stored in civicrm_event table, so you need to fetch the value and then compare it with the count of participants registered in this event. All this check should be done after a participant is created. So, you could use post hook for the same. Sample(not tested) code is shown below -

function example_civicrm_post($op, $objectName, $objectId, &$objectRef) {
  if ($op == 'create' && $objectName == 'Participant') {
    //check the count of participant in the event
    $participantCount = civicrm_api3('Participant', 'getcount', [
      'event_id' => $objectRef->event_id,
    ]); 

    //Compare it with the max participant value 
    $max = civicrm_api3('Event', 'getvalue', [
      'return' => "max_participants",
      'id' => 1,
    ]);

    //If max equals the count, send an email
    if ($max == $participantCount) {
      //send email to xyz@example.com
    }
  }
}