How can you check if a PHP session exists?

Question

Just wondering how to check if a PHP session exists... My understanding is that no matter what, if I am using sessions, I have to start my files with session_start() to even acc

Answer 1

isset($_SESSION) isn't sufficient because if a session has been created and destroyed (with session_destroy()) in the same execution, isset($_SESSION) will return true. And this situation may happen without your knowing about it when a 3rd party code is used. session_id() correctly returns an empty string, though, and can be called prior to session_start().