public function getGravatar($email = null)
    {
        if (isset($email)) {
            $this->setEmail((string)$email);
        }

        $url = self::BASE_URL;
        if ($this->secure) {
            $url = self::BASE_URL_SECURE;
        }

        $url .= $this->email;
        $url .= $this->extension;
        $url .= '?s=' . $this->size;
        $url .= '&d=' . $this->default;

        if ($this->forceDefault) {
            $url .= '&forcedefault=y';
        }

        $url .= '&rating=' . $this->rating;

        return $url;
    }