public function output($key)
    {
        $key = strtolower($key);

        $benchmark = $this->get($key);

        return sprintf('[%s] %s seconds, %sMB memory (%sMB peak)',
                $key,
                number_format($benchmark['avg_time'], 4),
                number_format($benchmark['avg_memory'], 2),
                number_format($benchmark['peak_memory'], 2)
            );
    }