How to get the real IP of the user client in PHP

How does PHP get the real IP of the user client? Obtaining the client's IP is actually not a simple task. Because of IP spoofing and proxy problems, the authenticity of obtaining the client's IP will be compromised and cannot be 100% accurate. However, we try to use more complete methods to obtain the customer's IP. Below, the editor will share with you the method of obtaining the real IP of the user's client in PHP. I hope it will be helpful to everyone.

Obtaining the client IP is actually not a simple task. Because there are IP spoofing and proxy problems, the authenticity of obtaining the client IP will be compromised and cannot be 100% accurate. But we still try our best to find it. A relatively complete method of obtaining the real IP of the client. You can find many methods of obtaining the IP using PHP.

function getIp(){
if (getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknown"))
$ip = getenv("HTTP_CLIENT_IP");
else if (getenv("HTTP_X_FORWARDED_FOR") && strcasecmp(getenv("HTTP_X_FORWARDED_FOR"), "unknown"))
$ip = getenv("HTTP_X_FORWARDED_FOR");
else if (getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR"), "unknown"))
$ip = getenv("REMOTE_ADDR");
else if (isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], "unknown"))
$ip = $_SERVER['REMOTE_ADDR'];
else
$ip = "unknown";
return($ip);

Now we need to explain this code. Two functions are used here, getenv() and strcasecmp( ), the previous function obtains the system environment variable. If the value can be obtained, it returns the value, otherwise it returns false.

$_SERVER is the server super global variable array, use $_SERVER['REMOTE_ADDR'] You can also get the client's IP address. The difference between the two is that getenv does not support php running in IIS isapi mode.

strcasecmp(string1,string2) The usage of the string function is to compare string1 and string2 , if equal, return 0. If string1 is greater than string2, return a number greater than 0. If it is less, return a number less than 0.

The function first uses the customer IP. If it is not established, try to use the proxy method. If it does not work, use it again. REMOTE_ADDR.

I have also seen a more detailed method of detecting IP, which takes into account IP spoofing and multiple proxy codes. The method is similar.

function getip() {
$unknown = 'unknown';
if ( isset($_SERVER['HTTP_X_FORWARDED_FOR']) && $_SERVER['HTTP_X_FORWARDED_FOR'] && strcasecmp($_SERVER['HTTP_X_FORWARDED_FOR'], $unknown) ) {
$ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
} elseif ( isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], $unknown) ) {
$ip = $_SERVER['REMOTE_ADDR'];
}
/*
处理多层代理的情况
或者使用正则方式：$ip = preg_match("/[\d\.]{7,15}/", $ip, $matches) ? $matches[0] : $unknown;
*/
if (false !== strpos($ip, ','))
$ip = reset(explode(',', $ip));
return $ip;
}

1. No proxy is used The server's PHP obtains the client IP:

REMOTE_ADDR = Client IP
HTTP_X_FORWARDED_FOR = No value or no display

2. When using a transparent proxy server ：Transparent Proxies

REMOTE_ADDR = Last proxy server IP
HTTP_X_FORWARDED_FOR = Client real IP (when passing through multiple proxy servers, this value is similar: 221.5.252.160, 203.98.182.163, 203.129. 72.215)

This type of proxy server still sends the client’s real IP to the access object, which cannot achieve the purpose of hiding the true identity.

3. Using ordinary anonymous proxy servers PHP obtains the client IP: Anonymous Proxies

REMOTE_ADDR = Last proxy server IP
HTTP_X_FORWARDED_FOR = Proxy server IP (when passing through multiple proxy servers, this value is similar: 203.98.182.163, 203.98 .182.163, 203.129.72.215)

In this case, the real IP of the client is hidden, but it is revealed to the access object that the client uses a proxy server to access them.

4. The use of deceptive proxy servers: Distorting Proxies

REMOTE_ADDR = Proxy server IP
HTTP_X_FORWARDED_FOR = Random IP (when passing through multiple proxy servers, this value is similar: 220.4. 251.159, 203.98.182.163, 203.129.72.215)

In this case, it is also revealed that the client uses a proxy server, but a fake random IP (220.4.251.159) is fabricated to replace the client’s real IP. Deceive it.

5. Use PHP of a high-anonymity proxy server to obtain the client IP: High Anonymity Proxies (Elite proxies)

REMOTE_ADDR = Proxy server IP

HTTP_X_FORWARDED_FOR = No value or not displayed

Whether it is REMOTE_ADDR or HTTP_FORWARDED_FOR, these header messages may not be available because different browsers and different network devices may send different IP header messages. Therefore, PHP The value obtained using $_SERVER["REMOTE_ADDR"] and $_SERVER["HTTP_X_FORWARDED_FOR"] may be a null value or an "unknown" value.

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