private function eventTokenEncode($values)
    {
        list($campaignId, $eventId, $contactId) = $values;
        $campaignIdString                       = $this->baseEncode((int) $campaignId);
        $eventIdString                          = $this->baseEncode((int) $eventId);
        $contactIdString                        = $this->baseEncode((int) $contactId);

        return $campaignIdString.'0'.$eventIdString.'0'.$contactIdString;
    }