Get client actual IP address - Based on HTTP headers - Detect Transparent proxy

client_ip.php

<?php

function get_client_ip()
{
    try {
        // Get real visitor IP behind CloudFlare network
        if (isset($_SERVER["HTTP_CF_CONNECTING_IP"])) {
            $_SERVER["REMOTE_ADDR"] = $_SERVER["HTTP_CF_CONNECTING_IP"];
            $_SERVER["HTTP_CLIENT_IP"] = $_SERVER["HTTP_CF_CONNECTING_IP"];
        }

        $ip_candidates = [
            $_SERVER["HTTP_CLIENT_IP"] ?? null,
            $_SERVER["HTTP_X_FORWARDED_FOR"] ?? null,
            $_SERVER["HTTP_FORWARDED_FOR"] ?? null,
            $_SERVER["HTTP_X_FORWARDED"] ?? null,
            $_SERVER["HTTP_FORWARDED"] ?? null,
            $_SERVER["HTTP_FORWARDED_FOR_IP"] ?? null,
            $_SERVER["X_FORWARDED_FOR"] ?? null,
            $_SERVER["FORWARDED_FOR"] ?? null,
            $_SERVER["CLIENT-IP"] ?? null,
            $_SERVER["FORWARDED_FOR_IP"] ?? null,
            $_SERVER["HTTP_X_APPENGINE_USER_IP"] ?? null,
            $_SERVER["HTTP_PROXY_CONNECTION"] ?? null,
            $_SERVER["HTTP_VIA"] ?? null,
            $_SERVER["VIA"] ?? null,
            $_SERVER["CF-Connecting-IP"] ?? null,
            $_SERVER["HTTP_X_REAL_IP"] ?? null,
            $_SERVER["CLIENT_IP"] ?? null,
            $_SERVER["HTTP_XROXY_CONNECTION"] ?? null,
            $_SERVER["HTTP_X_CLUSTER_CLIENT_IP"] ?? null,
            $_SERVER["CLIENT-IP"] ?? null,
            $_SERVER["HTTP_COMING_FROM"] ?? null,
            $_SERVER["HTTP_X_COMING_FROM"] ?? null,
            $_SERVER["MT-PROXY-ID"] ?? null,
            $_SERVER["X-PROXY-ID"] ?? null,
            $_SERVER["REMOTE_ADDR"] ?? null,
        ];

        foreach ($ip_candidates as $candidate) {
            if (is_null($candidate)) {
                continue;
            }

            $parts = explode(",", $candidate);

            if (empty($parts)) {
                continue;
            }

            $ip = preg_replace("/\s+/", "", $parts[0]);

            if (filter_var($ip, FILTER_VALIDATE_IP)) {
                return $ip; 
            }
        }
    } catch (Exception $ex) {
        return "Error";
    }

    return "UNKNOWN";
}

echo get_client_ip();
exit();

?>