The onFormatMessageVars handler is called on an array of $vars containing all of the variables about to be substituted into a notification message or email in the LiveWhale “messages” module. The example module below is abstracted from a need to overwrite certain variables in the RSVP “Registration Received” email.

<?php
     $_LW->REGISTERED_APPS['my_app']=[
       'title'=>'My App',
       'handlers'=>['onFormatMessageVars'],
    ];

    class LiveWhaleApplicationMyApp {

      public function onFormatMessageVars($vars) {
        global $_LW;

        // if this is a registration received message
        if (!empty($vars['registrations_url'])) {

            // do things..
            // e.g., edit $vars['date_time'] or any other notification variable
         
        }

        return $vars;
      }

   }
?>

This example uses the event_id (extracted from the end of ical_url) to add the group title for an event to an RSVP notification or confirmation email.

public function onFormatMessageVars($vars) {
  global $_LW;

  // if this is a registration received message
  if (!empty($vars['registrations_url'])) {

    // get event ID by pulling everything after last / in ical_url
    $event_id = substr($vars['ical_url'], strrpos($vars['ical_url'], '/') + 1); 
    
    // get event info corresponding to that ID
    $event_info = $_LW->read('events',['id'=>$event_id,'response_fields'=>'group_title']);
    
    // set group_title variable from the response
    $vars['group_title'] = (!empty($event_info[0]['group_title']) ? $event_info[0]['group_title'] : '');
  }

  return $vars;
}