正如所有其他人所说，你可以使用$_SERVER['REMOTE_ADDR'];获取客户端IP地址。

另外，如果你需要一个用户的更多信息，你可以使用这个:

<?php
    $ip = '0.0.0.0';
    $ip = $_SERVER['REMOTE_ADDR'];
    $clientDetails = json_decode(file_get_contents("http://ipinfo.io/$ip/json"));
    echo "You're logged in from: <b>" . $clientDetails->country . "</b>";
?>

客户端更具体的信息放在$clientDetails中。 $clientDetails->PostalCode/hostname/region/loc…

我用的是ipinfo。IO来获取额外的信息。

以下是我发现的最先进的方法，我在过去已经尝试过其他一些方法。确保获得访问者的IP地址是有效的(但请注意，任何黑客都很容易伪造IP地址)。

function get_ip_address() {

    // Check for shared Internet/ISP IP
    if (!empty($_SERVER['HTTP_CLIENT_IP']) && validate_ip($_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 $ip) {
                if (validate_ip($ip))
                    return $ip;
            }
        }
        else {
            if (validate_ip($_SERVER['HTTP_X_FORWARDED_FOR']))
                return $_SERVER['HTTP_X_FORWARDED_FOR'];
        }
    }
    if (!empty($_SERVER['HTTP_X_FORWARDED']) && validate_ip($_SERVER['HTTP_X_FORWARDED']))
        return $_SERVER['HTTP_X_FORWARDED'];
    if (!empty($_SERVER['HTTP_X_CLUSTER_CLIENT_IP']) && validate_ip($_SERVER['HTTP_X_CLUSTER_CLIENT_IP']))
        return $_SERVER['HTTP_X_CLUSTER_CLIENT_IP'];
    if (!empty($_SERVER['HTTP_FORWARDED_FOR']) && validate_ip($_SERVER['HTTP_FORWARDED_FOR']))
        return $_SERVER['HTTP_FORWARDED_FOR'];
    if (!empty($_SERVER['HTTP_FORWARDED']) && 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.
 */
function validate_ip($ip) {

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

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

    // 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;
}

获取客户端IP地址，请使用getenv("REMOTE_ADDR")。

例如,

$ip_address = getenv("REMOTE_ADDR");
echo $ip_address;

如果你使用localhost调用你的服务器，它会输出::1。 因此，请使用直接服务器ip地址或域名调用您的服务器。

快速解决方案(无错误)

function getClientIP():string
{
    $keys=array('HTTP_CLIENT_IP','HTTP_X_FORWARDED_FOR','HTTP_X_FORWARDED','HTTP_FORWARDED_FOR','HTTP_FORWARDED','REMOTE_ADDR');
    foreach($keys as $k)
    {
        if (!empty($_SERVER[$k]) && filter_var($_SERVER[$k], FILTER_VALIDATE_IP))
        {
            return $_SERVER[$k];
        }
    }
    return "UNKNOWN";
}

答案是使用$_SERVER变量。例如，$_SERVER["REMOTE_ADDR"]将返回客户端的IP地址。

function get_client_ip()
{
    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)) {
            foreach (explode(',', $_SERVER[$key]) as $ip) {
                $ip = trim($ip);
                if ((bool) filter_var($ip, FILTER_VALIDATE_IP,
                                FILTER_FLAG_IPV4 |
                                FILTER_FLAG_NO_PRIV_RANGE |
                                FILTER_FLAG_NO_RES_RANGE)) {
                    return $ip;
                }
            }
        }
    }
    return null;
}

或压缩版:

function get_ip() {
    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 (array_map('trim', explode(',', $_SERVER[$key])) as $ip) {
                if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false) {
                    return $ip;
                }
            }
        }
    }
}