How to solve the error of getting client IP in php

In the process of PHP programming, obtaining the client IP is a very common requirement. Obtaining the client IP is not a simple matter, and errors can easily occur. Today we will discuss common mistakes.

Mistake 1: Using $_SERVER['REMOTE_ADDR']

Beginners may use this common variable to obtain the client IP address:

$ip = $_SERVER['REMOTE_ADDR'];

This method is indeed The client IP can be obtained, but when the client accesses through the proxy server, this variable returns the IP address of the proxy server, not the client's real IP.

Error 2: Reusing $_SERVER['REMOTE_ADDR']

Another mistake is to reuse the $_SERVER['REMOTE_ADDR'] variable, that is, obtain it multiple times. This method will usually return the same IP because $_SERVER['REMOTE_ADDR'] is set when the request is processed.

$ip = $_SERVER['REMOTE_ADDR'];
$ip2 = $_SERVER['REMOTE_ADDR'];

Error 3: Obtaining wrong header information

You can view the request header information by accessing the following address:

http://httpbin.org/headers

In many tutorials, people use HTTP_X_FORWARDED_FOR or HTTP_CLIENT_IP to get the client IP address. However, this approach is not optimal as different proxy servers may use different identifiers for delivery.

This requires using the correct proxy server IP address in the server configuration file to ensure reliable acquisition of the client IP. Please see the code below for the specific method:

if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
    $ip = $_SERVER['HTTP_CLIENT_IP'];
} 
elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
} 
else {
    $ip = $_SERVER['REMOTE_ADDR'];
}

Error 4: Getting protocol error after proxy server

If you are working behind a proxy server and want to detect HTTP in PHP, the protocol is http or https, you can use the following code:

if (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off' || $_SERVER['SERVER_PORT'] == 443) {
    $protocol = 'https://';
} 
else {
    $protocol = 'http://';
}

Error five: Obtaining IP error in IIS server

If you are working in IIS server, use $_SERVER['REMOTE_ADDR'] to obtain the customer When entering the IP address, the following error may occur:

$_SERVER['REMOTE_ADDR'] returns 127.0.0.1 in IIS for local requests

There are also many ways to solve this problem, one of which is to use the following code:

if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
    $ip = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
    $ip = array_shift($ip);
} 
else {
    $ip = $_SERVER['REMOTE_ADDR'];
}

Summary

Correct Obtaining the client IP address accurately can be a headache, but it's crucial when dealing with sensitive data. The above errors are only a small part of the problems that may occur on a daily basis, but we can avoid these problems by mastering the correct methods and using server configuration files.

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