public function getValue()
    {
        static $ip = null;
        if ( is_null( $ip ) )
        {
            $ip = $this->getIpAddressFromProxy();

            // direct IP address
            if ( isset( $_SERVER[ 'REMOTE_ADDR' ] ) )
            {
                $ip = $_SERVER[ 'REMOTE_ADDR' ];
            }
        }

        return $ip;
    }