public static function format()
    {
        $format = null;

        if (count(self::accept('format')) == 1) {
            $mime = explode('/', key(self::accept('format')));
            $format = $mime[1];

            if ($pos = strpos($format, '+')) {
                $format = substr($format, 0, $pos);
            }

            //Format cannot be *
            if ($format == '*') {
                $format = null;
            }
        }

        if (self::has('request.format')) {
            $format = self::get('request.format', 'word');
        }

        return $format;
    }