Redirect anonymous users to custom URL I would like to implement a custom redirect for anonymous users that try to access a form built with FAPI. user_is_logged_in is used in access callback to provide true or false.

However, I couldn't find documentation on how to hook into access callback functionality e.g. what happens when it returns FALSE? Now it automatically redirects to default user login page but I need change this.
You can make the page available for all users, also anonymous, and in the page callback redirect the anonymous user to your custom page.