In this example, we generate a unique token using `uniqid()` and store it in the session. We then add the token to the form as a hidden input field and submit it to `process_form.php`. In `process_form.php`, we can check that the token submitted matches the one stored in the session to prevent CSRF attacks. This implementation does not require any external package library, as the `uniqid()` function is a built-in PHP function. However, there are various PHP packages and libraries available for implementing form tokens and other security measures, such as the `symfony/security` package or the `PHP-JWT` library.