phorge-phorge/src/applications/calendar/mail/PhabricatorCalendarReplyHandler.php

<?php

final class PhabricatorCalendarReplyHandler
  extends PhabricatorApplicationTransactionReplyHandler {

  public function validateMailReceiver($mail_receiver) {
    if (!($mail_receiver instanceof PhabricatorCalendarEvent)) {
      throw new Exception(
        pht(
          'Mail receiver is not a %s!',
          'PhabricatorCalendarEvent'));
    }
  }

  public function getObjectPrefix() {
    return 'E';
  }
}