php获得用户的真实IP

如果用户使用了代理服务器，真实ip就不在HTTP_CLIENT_IP头中，而需要通过http头HTTP_X_FORWARDED_FOR来解析了。

如下php函数：

function GetIP() { //获取IP
    if ($_SERVER["HTTP_X_FORWARDED_FOR"])
        $ip = $_SERVER["HTTP_X_FORWARDED_FOR"];
    else if ($_SERVER["HTTP_CLIENT_IP"])
        $ip = $_SERVER["HTTP_CLIENT_IP"];
    else if ($_SERVER["REMOTE_ADDR"])
        $ip = $_SERVER["REMOTE_ADDR"];
    else if (getenv("HTTP_X_FORWARDED_FOR"))
        $ip = getenv("HTTP_X_FORWARDED_FOR");
    else if (getenv("HTTP_CLIENT_IP"))
        $ip = getenv("HTTP_CLIENT_IP");
    else if (getenv("REMOTE_ADDR"))
        $ip = getenv("REMOTE_ADDR");
    else
        $ip = "Unknown";
    return $ip;
}
?>

php