我使用了其他答案之一，并添加了一些额外的东西，如CloudFlare代理和NGINX代理检测。

/**
 * Gets, validates and returns the connecting client's IP
 */
function getClientIP(){

    // Get real visitor IP behind CloudFlare network
    if (!empty($_SERVER["HTTP_CF_CONNECTING_IP"]) && validateIP($_SERVER['HTTP_CF_CONNECTING_IP'])) {
        return $_SERVER["HTTP_CF_CONNECTING_IP"];
    }

    // Get real visitor IP behind NGINX proxy - https://easyengine.io/tutorials/nginx/forwarding-visitors-real-ip/
    if (!empty($_SERVER["HTTP_X_REAL_IP"]) && validateIP($_SERVER['HTTP_X_REAL_IP'])) {
        return $_SERVER["HTTP_X_REAL_IP"];
    }

    // Check for shared Internet/ISP IP
    if (!empty($_SERVER['HTTP_CLIENT_IP']) && validateIP($_SERVER['HTTP_CLIENT_IP'])) {
        return $_SERVER['HTTP_CLIENT_IP'];
    }

    // Check for IP addresses passing through proxies
    if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {

        // Check if multiple IP addresses exist in var
        if (strpos($_SERVER['HTTP_X_FORWARDED_FOR'], ',') !== false) {
            $iplist = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
            foreach ($iplist as $ip) {
                if (validateIP($ip))
                    return $ip;
            }
        }
        else {
            if (validateIP($_SERVER['HTTP_X_FORWARDED_FOR']))
                return $_SERVER['HTTP_X_FORWARDED_FOR'];
        }
    }

    if (!empty($_SERVER['HTTP_X_FORWARDED']) && validateIP($_SERVER['HTTP_X_FORWARDED']))
        return $_SERVER['HTTP_X_FORWARDED'];

    if (!empty($_SERVER['HTTP_X_CLUSTER_CLIENT_IP']) && validateIP($_SERVER['HTTP_X_CLUSTER_CLIENT_IP']))
        return $_SERVER['HTTP_X_CLUSTER_CLIENT_IP'];

    if (!empty($_SERVER['HTTP_FORWARDED_FOR']) && validateIP($_SERVER['HTTP_FORWARDED_FOR']))
        return $_SERVER['HTTP_FORWARDED_FOR'];

    if (!empty($_SERVER['HTTP_FORWARDED']) && validateIP($_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.
 */
function validateIP($ip) {

    if (strtolower($ip) === 'unknown')
        return false;

    // Generate IPv4 network address
    $ip = ip2long($ip);

    // Do additional filtering on IP
    if(!filter_var($ip, FILTER_VALIDATE_IP))
        return false;

    // If the IP address is set and not equivalent to 255.255.255.255
    if ($ip !== false && $ip !== -1) {

        // Make sure to get unsigned long representation of IP address
        // due to discrepancies between 32 and 64 bit OSes and
        // signed numbers (ints default to signed in PHP)
        $ip = sprintf('%u', $ip);

        // Do private network range checking
        if ($ip >= 0 && $ip <= 50331647)
            return false;
        if ($ip >= 167772160 && $ip <= 184549375)
            return false;
        if ($ip >= 2130706432 && $ip <= 2147483647)
            return false;
        if ($ip >= 2851995648 && $ip <= 2852061183)
            return false;
        if ($ip >= 2886729728 && $ip <= 2887778303)
            return false;
        if ($ip >= 3221225984 && $ip <= 3221226239)
            return false;
        if ($ip >= 3232235520 && $ip <= 3232301055)
            return false;
        if ($ip >= 4294967040)
            return false;
    }
    return true;
}

我在生产节点中使用它，它工作得很好。由于大部分代码来自这里，我已经在GNU @ https://github.com/d3vdigital/whatsmyip-node下发布了一个节点

在PHP中，获取公共IP的最后一个选项应该始终是$_SERVER["REMOTE_ADDR"]，因为有太多的安全原因。

下面是获取客户端已验证的IP地址的变通方法。

public static function getPublicIP() : string
    {
        $realIP = "Invalid IP Address";

        $activeHeaders = [];

        $headers = [
            "HTTP_CLIENT_IP",
            "HTTP_PRAGMA",
            "HTTP_XONNECTION",
            "HTTP_CACHE_INFO",
            "HTTP_XPROXY",
            "HTTP_PROXY",
            "HTTP_PROXY_CONNECTION",
            "HTTP_VIA",
            "HTTP_X_COMING_FROM",
            "HTTP_COMING_FROM",
            "HTTP_X_FORWARDED_FOR",
            "HTTP_X_FORWARDED",
            "HTTP_X_CLUSTER_CLIENT_IP",
            "HTTP_FORWARDED_FOR",
            "HTTP_FORWARDED",
            "ZHTTP_CACHE_CONTROL",
            "REMOTE_ADDR" #this should be the last option
        ];

        #Find active headers
        foreach ($headers as $key)
        {
            if (array_key_exists($key, $_SERVER))
            {
                $activeHeaders[$key] = $_SERVER[$key];
            }
        }

         #Reemove remote address since we got more options to choose from
        if(count($activeHeaders) > 1)
        {
            unset($activeHeaders["REMOTE_ADDR"]);
        }

        #Pick a random item now that we have a secure way.
        $realIP = $activeHeaders[array_rand($activeHeaders)];

        #Validate the public IP
        if (filter_var($realIP, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4))
        {
            return $realIP;
        }

        return $realIP;
    }

正如您在这里看到的，$_SERVER["REMOTE_ADDR"]是IP的最后一个选项。在收到IP后，我们也验证IP，以确保质量和安全。

其中之一:

    $ip = $_SERVER['REMOTE_ADDR'];
    $ip = $_SERVER['HTTP_CLIENT_IP'];
    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
    $ip = $_SERVER['HTTP_X_FORWARDED'];
    $ip = $_SERVER['HTTP_FORWARDED_FOR'];
    $ip = $_SERVER['HTTP_FORWARDED'];

你可以使用下面的函数

function get_client_ip() {
    $ipaddress = '';
    if (isset($_SERVER['HTTP_CLIENT_IP']))
        $ipaddress = $_SERVER['HTTP_CLIENT_IP'];
    else if(isset($_SERVER['HTTP_X_FORWARDED_FOR']))
        $ipaddress = $_SERVER['HTTP_X_FORWARDED_FOR'];
    else if(isset($_SERVER['HTTP_X_FORWARDED']))
        $ipaddress = $_SERVER['HTTP_X_FORWARDED'];
    else if(isset($_SERVER['HTTP_FORWARDED_FOR']))
        $ipaddress = $_SERVER['HTTP_FORWARDED_FOR'];
    else if(isset($_SERVER['HTTP_FORWARDED']))
        $ipaddress = $_SERVER['HTTP_FORWARDED'];
    else if(isset($_SERVER['REMOTE_ADDR']))
        $ipaddress = $_SERVER['REMOTE_ADDR'];
    else
        $ipaddress = 'UNKNOWN';
    return $ipaddress;
}

echo $_SERVER['REMOTE_ADDR'];

http://php.net/manual/en/reserved.variables.server.php

这个函数很紧凑，可以在任何地方使用。但是!

别忘了这一点!在这类函数或代码块中，不能保证记录用户的真实IP地址，因为有些用户可以使用代理或其他安全网关来实现不可见或无法跟踪

PHP函数:

function GetIP()
{
    if ( getenv("HTTP_CLIENT_IP") ) {
        $ip = getenv("HTTP_CLIENT_IP");
    } elseif ( getenv("HTTP_X_FORWARDED_FOR") ) {
        $ip = getenv("HTTP_X_FORWARDED_FOR");
        if ( strstr($ip, ',') ) {
            $tmp = explode(',', $ip);
            $ip = trim($tmp[0]);
        }
    } else {
        $ip = getenv("REMOTE_ADDR");
    }
    return $ip;
}

用法:

$IP = GetIP();或直接GetIP();