public static function format_header ($info) {
		if (is_array ($info['message'])) {
			$extra = array (
				'Type' => self::$log_levels[$info['level']],
				'File' => $info['message'][1],
				'Line' => $info['message'][2]
			);
			$info['message'] = $info['message'][0];
		} else {
			$extra = array ('Type' => self::$log_levels[$info['level']]);
		}

		$json = json_encode (array ($extra, $info['message']));

		return sprintf ('X-Wf-1-1-1-%d: %s|%s|', self::$message_index++, strlen ($json), $json);
	}