How do I determine the client IP type (IPv4/IPv6) in PHP

In the PHP, there are filters which can determine IPv4 and IPv6: FILTER_VALIDATE_IP, FILTER_FLAG_IPV4, FILTER_FLAG_IPV6.

Below code shows how to determine the client protocol:

<?php
// Get the client's IP address
$clientIP = $_SERVER['REMOTE_ADDR'];

// Check if it's an IPv6 address
if (filter_var($clientIP, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
    echo "Client is using IPv6";
} 
// Check if it's an IPv4 address
elseif (filter_var($clientIP, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
    echo "Client is using IPv4";
} 
// If it's neither IPv4 nor IPv6
else {
    echo "Unknown IP address type";
}

This code snippet checks whether the client's IP address is IPv4 or IPv6 using filter_var() function with FILTER_VALIDATE_IP flag. If it's a valid IPv6 address, it prints "Client is using IPv6". If it's a valid IPv4 address, it prints "Client is using IPv4". If it's neither IPv4 nor IPv6, it prints "Unknown IP address type".