Convert IP address to longint in PHP

IPToLong.php

<?php
/**
 * IP to long
 * @param type $ip
 * @return int
 */
function ipToLong($ip = false) {
    if (!$ip) {
        $ip = getClientIPAddress();
    }
    $ip2long = ip2long($ip);
    if ($ip2long < 0) {
        $ip2long = sprintf('%u', $ip2long);
    }

    return $ip2long;
}

/**
 * Retuns client's IP address
 * @return string
 * @since 6/16/11 12:11 PM
 */
function getClientIPAddress() {
    if (getenv("HTTP_CLIENT_IP")) {
        $ip = getenv("HTTP_CLIENT_IP");
    } else {
        if (getenv("HTTP_X_FORWARDED_FOR")) {
            $ip = getenv("HTTP_X_FORWARDED_FOR");
        } else {
            if (getenv("REMOTE_ADDR")) {
                $ip = getenv("REMOTE_ADDR");
            } else {
                $ip = "UNKNOWN";
            }
        }
    }

    return $ip;
}