Documentation on session refers to rules from a topic that does not exist any more?

From manual page: https://php.net/intro.session

The documentation says "Serialize handlers (php and php_binary) inherit register_globals limitations." But as I understand the "register_globals" feature/topic/documentation does not exist any more. I think that documentation section on rules for keys names could be done in a more clear and explicit manner e.g. using bullet list of things that are not allowed. Also it is not clear if these rules apply only "root" level entries in $_SESSION or also for nested data.
Because all of these issues I am not sure if I see here the complete list of rules, or perhaps there is something more under "inheregister_globals limitations" topic, that I cannot find.

Start with the session manual page at https://php.net/intro.session and investigate the reference to register_globals and the stated key-name rules. Check the surrounding documentation and available PHP behavior to determine whether the rules still apply, whether they cover nested session data, and what the complete documented list should be. Done means the page no longer points to a nonexistent topic and clearly states the applicable rules.