parseStr($template); $template = $DOM->query('body'); $data = Links::DATA_TAG; // do not encode data; it's replaced with subscriber-specific data // and encoded during send operation (Links::replaceSubscriberData()) $url = API::buildRequest( TrackAPI::ENDPOINT, TrackAPI::ACTION_OPEN, $data, $encode_data = false ); $open_tracking_image = sprintf( '', $url ); $template->html($template->html() . $open_tracking_image); return $DOM->__toString(); } static function addTrackingImage() { add_filter(Renderer::POST_PROCESS_FILTER, function($template) { return OpenTracking::process($template); }); return true; } }