parseStr($template); $template = $DOM->query('body'); $open_tracking_image = sprintf( '', home_url(), esc_attr('?mailpoet&endpoint=track&action=open&data=' . Links::DATA_TAG) ); $template->html($template->html() . $open_tracking_image); return $DOM->__toString(); } static function addTrackingImage() { add_filter('mailpoet_rendering_post_process', function ($template) { return OpenTracking::process($template); }); } }