protected function dsn_string($dsn)
    {
        $params = array();
        $result = 'mysql:';

        if ($dsn['database']) {
            $params[] = 'dbname=' . $dsn['database'];
        }

        if ($dsn['hostspec']) {
            $params[] = 'host=' . $dsn['hostspec'];
        }

        if ($dsn['port']) {
            $params[] = 'port=' . $dsn['port'];
        }

        if ($dsn['socket']) {
            $params[] = 'unix_socket=' . $dsn['socket'];
        }

        $params[] = 'charset=utf8';

        if (!empty($params)) {
            $result .= implode(';', $params);
        }

        return $result;
    }