KSST / KF

     *

     * @return string String denoting the user agent being which is accessing the page.

     */

    public static function getUserAgent()

    {

        $ua          = strip_tags($_SERVER['HTTP_USER_AGENT']);

        $ua_filtered = filter_var($ua, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW | FILTER_FLAG_STRIP_HIGH);

        return $ua_filtered;

    }

    /**

     * Returns the Referrer ($_SERVER HTTP_REFERER).

     *

     * @return string The address of the page (if any) which referred the user agent to the current page.

     */

    public static function getReferer()

    {

        if ($_SERVER['HTTP_REFERER'] !== null) {

            $refr          = strip_tags($_SERVER['HTTP_REFERER']);

            $refr_filtered = filter_var($refr, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW | FILTER_FLAG_STRIP_HIGH);

        }

        return $refr_filtered;

    }

    /**

     * Validates a given IP.