function getUserIP() {
    // Check if the 'HTTP_X_FORWARDED_FOR' header exists (used when behind a proxy or load balancer)
    if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        // This may contain multiple IPs, so split by comma and get the first one
        $ip = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR'])[0];
    }
    // If the above header doesn't exist, fall back to 'REMOTE_ADDR'
    elseif (!empty($_SERVER['HTTP_CLIENT_IP'])) {
        $ip = $_SERVER['HTTP_CLIENT_IP'];
    } else {
        $ip = $_SERVER['REMOTE_ADDR'];
    }

    return $ip;
}