public function getUrlForHash($hash, $size = null, $rating = null, $default = null, $secure = null)
    {
        $map = array(
            's' => $size ?: $this->defaults['size'],
            'r' => $rating ?: $this->defaults['rating'],
            'd' => $default ?: $this->defaults['default'],
        );

        if (null === $secure) {
            $secure = $this->defaults['secure'];
        }

        return ($secure ? 'https://secure' : 'http://www') . '.gravatar.com/avatar/' . $hash . '?' . http_build_query(array_filter($map));
    }