Getting real IP address from AWS LB

aws_lb_real_ip.txt

function getClientIP()
{
    if ($_SERVER['HTTP_X_FORWARDED_FOR']) {
        $ip_exp = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
        $c = count($ip_exp) - 1;
        $real_ip = trim($ip_exp[$c]);
        return $_SERVER['REMOTE_ADDR'] = $real_ip;
    } else {
        return $_SERVER['REMOTE_ADDR'];
    }
}

$client_ip = getClientIP();
echo $client_ip;