Cache-Key Warning with Stack Trace

Bit Form Bugs
1

Bit Form Pro – Cache Key Empty String Warning

Issue Summary

On our development environment (WordPress 6.7.2, PHP 8.2), we are seeing the following warning at the top of the Bit Forms admin page:


Notice: Function WP_Object_Cache::add was called incorrectly. Cache key must not be an empty string. Please see Debugging in WordPress for more information. (This message was added in version 6.1.0.) in /Users/chrisconlee/Documents/pifster.local/wp-includes/functions.php on line 6121

Steps to Reproduce

  1. Log in to WordPress admin.

  2. Navigate to the Bit Forms admin page.

  3. The above notice appears at the top of the page.

Environment

  • WordPress Version: 6.7.2

  • PHP Version: 8.2

  • Bit Form Pro Version: 2.12.6 (standard version 218.8)

  • Theme: Breakdance Zero Child

Debugging Actions Taken

  • Enabled WP_DEBUG and WP_DEBUG_LOG in wp-config.php.

  • Added a temporary shutdown handler to capture a stack trace when the warning occurs.

Captured Notice and Stack Trace


[01-May-2025 18:34:10 UTC] PHP Notice: Function WP_Object_Cache::add was called incorrectly. Cache key must not be an empty string. Please see Debugging in WordPress for more information. (This message was added in version 6.1.0.) in /Users/chrisconlee/Documents/pifster.local/wp-includes/functions.php on line 6121

[01-May-2025 18:34:11 UTC] === WP_Object_Cache::add Stack Trace ===

[01-May-2025 18:34:11 UTC] #0 /Users/chrisconlee/Documents/pifster.local/wp-includes/class-wp-hook.php(324): {closure}('')

#1 /Users/chrisconlee/Documents/pifster.local/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)

#2 /Users/chrisconlee/Documents/pifster.local/wp-includes/plugin.php(517): WP_Hook->do_action(Array)

#3 /Users/chrisconlee/Documents/pifster.local/wp-includes/load.php(1304): do_action('shutdown')

#4 [internal function]: shutdown_action_hook()

[01-May-2025 18:34:11 UTC] === End Stack Trace ===

Additional Notes

  • The stack trace was captured using a shutdown handler in the theme’s functions.php.

  • No additional plugin or theme code is referenced in the trace, so the original source of the empty cache key is not visible.

  • The issue does not appear to break site functionality, but it does indicate a bug in plugin or theme code using wp_cache_add() (or similar) with an empty string as the cache key.

Request

  • Please advise on how to further trace the origin of this warning, or provide a patch to ensure all cache keys are non-empty when using WordPress object cache functions.

  • Let us know if you need more information or if you would like us to test a debug version for deeper tracing.

Prepared by the PIFster development team – May 1, 2025