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Block a List of IP Addresses in PHP

Nathan's photo
Nathan
·Sep 18, 2021·

1 min read

Here's a simple PHP snippet that you can place at the top of a file to determine whether the IPv4 address of a request is blacklisted:

$blacklist = array(
    '127.0.0.1',
    '192.168.1.1',
    // etc.
);

$ip = isset($_SERVER['REMOTE_ADDR']) ? trim($_SERVER['REMOTE_ADDR']) : '';

if (($key = array_search($ip, $blacklist)) !== false) {
    echo 'You are forbidden from accessing this resource!';
    exit();
}

// If the process has not exited, then the IP address is not blacklisted.

You could also pull a list of IP addresses from a file:

    $blacklist = file('blacklist.txt', FILE_IGNORE_NEW_LINES);

In the above example, each line of blacklist.txt should contain a single and unique IP address.

Adding a 403 response code

If you haven't already, you might want to consider responding with a 403 error:

http_response_code(403);
echo trim('
    <!DOCTYPE html><html><head><title>403</title></head><body>You are forbidden from accessing this resource!</body></html>
');
exit();

Conclusion

Anyway, this is just one of many simple ways to block a list of IP addresses from accessing a resource on your PHP server.

If you're running into issues, remember to add this snippet to the top of the files you want to add it to!