我知道有大量的$_SERVER变量头可用于检索IP地址。我想知道是否有一个普遍共识，即使用这些变量哪种方法可以最准确地检索用户的真实IP地址（明确知道没有任何一种方法是完美的）？
我花了一些时间尝试找到一个深入的解决方案，并根据多个来源得出了以下代码。如果有人能够发现漏洞或者介绍更准确的方法，我会很感激。
编辑包括@Alix的优化
/**
* Retrieves the best guess of the client's actual IP address.
* Takes into account numerous HTTP proxy headers due to variations
* in how different ISPs handle IP addresses in headers between hops.
*/
public function get_ip_address() {
// Check for shared internet/ISP IP
if (!empty($_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 = $ip;
return true;
}
警告（更新）
REMOTE_ADDR仍然表示IP地址的最可靠的来源。在此提到的其他$_SERVER变量可以很容易地被远程客户端欺骗。此解决方案的目的是尝试确定代理后面的客户端的IP地址。对于一般目的，您可以考虑将其与直接从 $_SERVER['REMOTE_ADDR'] 返回的IP地址结合使用并存储两者。
对于99.9%的用户，此解决方案将完全满足您的需求。它无法防范那些通过注入自己的请求头来滥用系统的0.1%的恶意用户。如果依赖IP地址进行关键任务，请使用REMOTE_ADDR，不必担心那些使用代理的用户。