Initial assessment
WordPress Error Cases

Fatal error: Uncaught Error: Call to undefined function …

“Call to undefined function” in WordPress after a PHP upgrade: causes and what to check

Updated 2026-10-31
# Common log entries
PHP Fatal error:  Uncaught Error: Call to undefined function create_function() in …/wp-content/plugins/…

PHP throws this error when code calls a function that does not exist in the running PHP version or its extensions. On WordPress sites it often appears after the host moves the site to PHP 8.

Which of these matches what you see?

Functions removed in PHP 8, such as create_function() and each(), stop older plugin or theme code. The error names the function and the file.

The new PHP build lacks an extension the site uses. The hosting control panel lists which extensions are enabled for each PHP version.

The new plugin version calls a function from another plugin, or from a newer WordPress release than the site runs.

Common causes

Functions removed in PHP 8: create_function(), each(), and other functions no longer exist.
Missing PHP extension: The new PHP build lacks mysqli, imagick, ionCube Loader, or another extension the site uses.
Plugin dependency: The code expects another plugin or a newer WordPress version.
Older theme code: Theme code written for PHP 5 or 7 has not been updated.

References

  1. PHP documentation: migrating from PHP 7.4 to PHP 8.0
  2. Debugging in WordPress (Advanced Administration Handbook)

What the system does

White screens and fatal errors (plugin conflicts, PHP version incompatibility) are handled automatically: on a copy of your site in the recovery station, the system turns on debug mode, finds the plugin or theme causing the error and deactivates it (not deleted). Deactivated plugins are listed in the recovery report; whether to re-enable them is your decision. Fixes are made on a copy of your site in the recovery station and written back only after re-verification passes. In your site’s database, the protected tables (members, comments, orders and form submissions) are copied as structure only. In SSH and FTP mode, the system creates a pre-recovery backup on your host before writing back and restores from it if verification after write-back fails. If the recovery cannot be completed, the recovery fee is refunded in full.

  1. Initial assessment: Enter the site URL
  2. Copy to the recovery station: Work runs on the copy
  3. Find the cause: Item-by-item checks
  4. Recover and re-check: Home and inner pages
  5. Write back or deliver: Only after re-checks pass

Use WP119 when the error names a plugin or theme file and the dashboard does not load.

Assess my site →
Initial assessment →