get_client_ip

/**
 * @author chenliujin <[email protected]>
 * @since 2014-04-17
 */
function get_client_ip()
{
    $checks = array(
        'HTTP_X_FORWARDED_FOR',
        'HTTP_X_FORWARDED',
        'HTTP_FORWARDED_FOR',
        'HTTP_FORWARDED',
        'HTTP_VIA',
        'HTTP_X_COMING_FROM',
        'HTTP_COMING_FROM',
        'HTTP_CLIENT_IP',
        'X-Real-IP',
        'HTTP_X_REAL_IP',
    );

    foreach ($checks as $check) {
        if (isset($_SERVER[$check])) {
            $ip = $_SERVER[$check];

            if (($pos = strpos($ip, ',')) != FALSE) {
                $ip = substr($ip, 0, $pos);
            }

            $ipnum = ip2long($ip);

            if ($ipnum !== -1 && $ipnum !== FALSE && long2ip($ipnum) === $ip) {
                if (($ipnum < 167772160 || $ipnum > 184549375) && ($ipnum < - 1408237568 || $ipnum > - 1407188993) && ($ipnum < - 1062731776 || $ipnum > - 1062666241))
                    return $ip;
            }

        }
    }

    return $_SERVER['REMOTE_ADDR'];
}

1.HTTP_X_REAL_IP or HTTP_X_FORWARDED_FOR?

http://gtranslate.net/forum/http-real-http-forwarded-for-t2980.html

2. http://www.cnblogs.com/lmule/archive/2010/10/15/1852020.html