Description

This PR addresses an inconsistency in the wp_using_ext_object_cache() function where it could return null instead of the documented bool type.

In src/wp-includes/load.php, the global variable $_wp_using_ext_object_cache is used to determine if an external object cache is in use. However, if this function is called early in the WordPress loading hierarchy (before the global is initialized), it currently returns null.

With the ongoing efforts to make WordPress more compatible with PHP 8.x strict typing, ensuring deterministic return types is critical to prevent TypeError or unexpected behavior in downstream logic.

Key Changes:

• I maintained the original 'get-before-set' return pattern to ensure backward compatibility for developers who rely on the returned value to restore previous states.
• By casting $current_using to (bool), we resolve the issue where an uninitialized global variable causes the function to leak a null value.

Testing Instructions

1. Run an isolated script to call wp_using_ext_object_cache() before the global variable is initialized (e.g., before wp-settings.php is fully loaded).
2. Before Patch: The function returns NULL.
3. After Patch: The function returns bool(false).

Trac ticket: https://core.trac.wordpress.org/ticket/64950

Use of AI Tools

AI assistance: Yes
Tool(s): Google Gemini
Model(s): Gemini 3 Flash
Used for: Authoring the technical description and formatting the testing instructions based on my code implementation. The code logic and testing methodology were reviewed and verified by me.

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.