<?php

function client_ip()

{

    if(isset($_SERVER['HTTP_X_REAL_IP'])) {

        return $_SERVER['HTTP_X_REAL_IP'];

    } else {

        if (!empty($_SERVER['HTTP_CLIENT_IP'])) {

            return $_SERVER['HTTP_CLIENT_IP'];

        } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {

            return $_SERVER['HTTP_X_FORWARDED_FOR'];

        } else {

            return $_SERVER['REMOTE_ADDR'];

        }

    }

}

?>



Вывод на экран:

<?php

echo client_ip();

?>