A better way to detect IP in PHP

Sometimes we cannot get the correct IP of the client by $_SERVER['REMOTE_ADDR'], so we need the following function!

<?php
function getrealip()
{
    $ip = FALSE;
    if (!empty($_SERVER["HTTP_CLIENT_IP"])) {
        $ip = $_SERVER["HTTP_CLIENT_IP"];
    }

    if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        $ips = explode (", ", $_SERVER['HTTP_X_FORWARDED_FOR']);
        if ($ip) {
            array_unshift($ips, $ip);
            $ip = FALSE;
        }

        for ($i = 0; $i < count($ips); $i++) {
            if (!eregi ("^(10|172\.16|192\.168)\.", $ips[$i])) {
                if (version_compare(phpversion(), "5.0.0", ">=")) {
                    if (ip2long($ips[$i]) != false) {
                        $ip = $ips[$i];
                        break;
                    }
                } else {
                    if (ip2long($ips[$i]) != -1) {
                        $ip = $ips[$i];
                        break;
                    }
                }
            }
        }
    }
    return ($ip ? $ip : $_SERVER['REMOTE_ADDR']);
}
?>