wp_get_current_user() and is_user_logged_in() in child theme's functions.php file don't work

Question

Is there any reason why wp_get_current_user() doesn't return the logged in user's info array when used within functions.php file in a child theme, nor does the is_user_logged_in() return the correct state for a logged in user? They both return 0 regardless if the user is logged in or not.

I am embedding the wordpress libraries into a 3rd party script and everything, literally everything else works outside of wordpress on a separate PHP page but this.

Answer 1

It could be due to a hook firing sequence issue. When are you hooking your function?

The safest way to detect your current user is to fire on wp_login action. Someone reported the need to call it late.

The codex recommends to use wp_get_current_user() functon on or after the init hook.