在PHP中检索用户正确IP地址的最准确方法是什么？

Question

我知道有太多的 $ _SERVER
变量标头可用于IP地址检索。我想知道是否就使用上述变量最准确地检索用户的真实IP地址（众所周知没有一种方法是完美的）是否达成共识？

我花了一些时间试图找到一个深入的解决方案，并根据许多资源提出了以下代码。如果有人可以在答案中戳出一个洞或阐明一些可能更准确的内容，我将非常喜欢。

编辑包括来自@Alix的优化

 /**
  * Retrieves the best guess of the client's actual IP address.
  * Takes into account numerous HTTP proxy headers due to variations
  * in how different ISPs handle IP addresses in headers between hops.
  */
 public function get_ip_address() {
  // Check for shared internet/ISP IP
  if (!empty($_SERVER['HTTP_CLIENT_IP']) && $this->validate_ip($_SERVER['HTTP_CLIENT_IP']))
   return $_SERVER['HTTP_CLIENT_IP'];

  // Check for IPs passing through proxies
  if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
   // Check if multiple IP addresses exist in var
    $iplist = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
    foreach ($iplist as $ip) {
     if ($this->validate_ip($ip))
      return $ip;
    }
   }
  }
  if (!empty($_SERVER['HTTP_X_FORWARDED']) && $this->validate_ip($_SERVER['HTTP_X_FORWARDED']))
   return $_SERVER['HTTP_X_FORWARDED'];
  if (!empty($_SERVER['HTTP_X_CLUSTER_CLIENT_IP']) && $this->validate_ip($_SERVER['HTTP_X_CLUSTER_CLIENT_IP']))
   return $_SERVER['HTTP_X_CLUSTER_CLIENT_IP'];
  if (!empty($_SERVER['HTTP_FORWARDED_FOR']) && $this->validate_ip($_SERVER['HTTP_FORWARDED_FOR']))
   return $_SERVER['HTTP_FORWARDED_FOR'];
  if (!empty($_SERVER['HTTP_FORWARDED']) && $this->validate_ip($_SERVER['HTTP_FORWARDED']))
   return $_SERVER['HTTP_FORWARDED'];

  // Return unreliable IP address since all else failed
  return $_SERVER['REMOTE_ADDR'];
 }

 /**
  * Ensures an IP address is both a valid IP address and does not fall within
  * a private network range.
  *
  * @access public
  * @param string $ip
  */
 public function validate_ip($ip) {
     if (filter_var($ip, FILTER_VALIDATE_IP, 
                         FILTER_FLAG_IPV4 | 
                         FILTER_FLAG_IPV6 |
                         FILTER_FLAG_NO_PRIV_RANGE | 
                         FILTER_FLAG_NO_RES_RANGE) === false)
         return false;
     self::$ip = $ip;
     return true;
 }

警告语（更新）

REMOTE_ADDR仍然代表IP地址的 最可靠
来源。$_SERVER远程客户端很容易欺骗这里提到的其他变量。该解决方案的目的是尝试确定位于代理后面的客户端的IP地址。为了您的一般目的，您可以考虑将其与直接从$_SERVER['REMOTE_ADDR']两者存储并返回的IP地址结合使用。

对于99.9％的用户，此解决方案将完全满足您的需求。
它不会通过注入自己的请求标头来保护您免受0.1％恶意用户滥用系统的侵害。如果依靠IP地址执行某些关键任务，请诉诸于REMOTE_ADDR代理，而不必理会这些代理。

Answer 1

这是获取IP地址的更短，更简洁的方法：

function get_ip_address(){
    foreach (array('HTTP_CLIENT_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED', 'REMOTE_ADDR') as $key){
        if (array_key_exists($key, $_SERVER) === true){
            foreach (explode(',', $_SERVER[$key]) as $ip){
                $ip = trim($ip); // just to be safe

                if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false){
                    return $ip;
                }
            }
        }
    }
}

希望对您有所帮助！

您的代码似乎已经很完整了，我看不到其中的任何可能的错误（除了常见的IP警告），validate_ip()尽管如此，我还是将功能更改为依赖过滤器扩展：

public function validate_ip($ip)
{
    if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) === false)
    {
        return false;
    }

    self::$ip = sprintf('%u', ip2long($ip)); // you seem to want this

    return true;
}

您的HTTP_X_FORWARDED_FOR代码段也可以从此简化：

// check for IPs passing through proxies
if (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
{
    // check if multiple ips exist in var
    if (strpos($_SERVER['HTTP_X_FORWARDED_FOR'], ',') !== false)
    {
        $iplist = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);

        foreach ($iplist as $ip)
        {
            if ($this->validate_ip($ip))
                return $ip;
        }
    }

    else
    {
        if ($this->validate_ip($_SERVER['HTTP_X_FORWARDED_FOR']))
            return $_SERVER['HTTP_X_FORWARDED_FOR'];
    }
}

对此：

// check for IPs passing through proxies
if (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
{
    $iplist = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);

    foreach ($iplist as $ip)
    {
        if ($this->validate_ip($ip))
            return $ip;
    }
}

您可能还需要验证IPv6地址。