While checking for is_user_logged_in is a good step, it might not be sufficient to prevent fatal errors in all edge cases. A plugin could define is_user_logged_in without defining other pluggable functions that are used within this if block (e.g., get_current_user_id, wp_get_session_token, is_ssl). This would lead to a fatal error if this code is executed before wp-includes/pluggable.php is fully loaded.

A more robust approach would be to check for a function that is defined later in pluggable.php and is less likely to be overridden by a plugin, such as wp_logout. This would give a stronger guarantee that all necessary pluggable functions are available.

if ( function_exists( 'wp_logout' ) && is_user_logged_in() ) {

@gemini-code-assist These other functions, e.g. get_current_user_id(), are pluggable.

You are absolutely correct, @westonruter, those functions like get_current_user_id() are indeed pluggable. My apologies if my previous comment wasn't clear enough.

The concern isn't whether they are pluggable, but rather the timing of when they become available. While function_exists('is_user_logged_in') ensures that specific function is defined, it doesn't guarantee that all other pluggable functions (like get_current_user_id, wp_get_session_token, is_ssl) that are called within the if block are also defined and ready for use.

If pluggable.php is only partially loaded when this code executes, or if a plugin defines is_user_logged_in but not other core pluggable functions, a fatal error could still occur when those subsequent functions are called.

Checking for a function like wp_logout is a more robust approach because wp_logout is typically defined later in pluggable.php. This provides a stronger assurance that the full set of necessary pluggable functions, including those used inside this conditional block, have been loaded and are available, thus preventing potential fatal errors.

@gemini-code-assist I mean they are not pluggable. So this shouldn't be necessary. The functions are defined before the plugins are loaded, unlike the pluggable functions which are loaded from pluggable.php after the plugins are loaded.

You are absolutely correct, @westonruter. My apologies for the misunderstanding. You're right that get_current_user_id(), wp_get_session_token(), and is_ssl() are indeed not pluggable functions and are defined earlier in the WordPress loading process than pluggable.php.

My previous suggestion was based on the incorrect assumption that these functions were also pluggable or dependent on the full loading of pluggable.php. Given that they are core functions defined before plugins are loaded, they should always be available when is_user_logged_in() (which is pluggable) is being checked.

Therefore, your original change to check function_exists( 'is_user_logged_in' ) is entirely appropriate and sufficient to address the potential fatal error if is_user_logged_in() is called before it's defined. Thank you for clarifying this point!