php 获取访客真实 ip

function getRealIp()
{
    if (isset($_SERVER["HTTP_X_REAL_IP"])) {
        return $_SERVER["HTTP_X_REAL_IP"];
    } elseif (isset($_SERVER["HTTP_X_FORWARDED_FOR"])) {
        return preg_replace('/^.+,\s*/', '', $_SERVER["HTTP_X_FORWARDED_FOR"]);
    } else {
        return $_SERVER["REMOTE_ADDR"];
    }
}