Fatal is_admin_bar_showing() - Call to undefined function is_user_logged_in()

[kkmuffme]

When hooking a callback on e.g. "muplugins_loaded" or on "shutdown" from an mu-plugin, object cache or advanced cache and checking "is_admin_bar_showing()", you can get a fatal bc pluggable.php which is called isn't loaded yet.

Either add a function exists check for "is_user_logged_in" or load pluggable.php early?

[dd32]

Calling certain functions before init runs is not advised, and can lead to fatal errors like you've experienced.

muplugins_loaded shouldn't be anything other than the very first plugin bootstrap functionality (such as adding filters), The WordPress user is not loaded at that time (So you can't check if a user setting is valid), and shutdown occurs after the page may be output to the browser.

To me, it feels like the code you're running might be the problem, and should be delayed until init or later.

Can you provide example code that shows the behaviour in a way which should be supported?

[kkmuffme]

shutdown occurs after the page may be output to the browser.

shutdown also happens if there's an uncaught exception for example, in which case there will never be an "init" hook if the exception happens before that.

EDIT: when WP loads a function, it needs to make sure that all things it calls have been loaded already or it will load them itself

EDIT2: or if an (mu-)plugin or theme calls exit, shutdown is called long before the init hook.

[sabernhardt]

is_admin_bar_showing() runs the is_user_logged_in() condition if $show_admin_bar is not set (after checking whether it is an XML-RPC/Ajax/iframe/JSON request, an embed, or within the admin).

Could you use show_admin_bar( false ); somehow?

[kkmuffme]

I already worked around this issue in my code without modifying any global states, however this is something that should be addressed in WP core.