Initial assessment
Common WordPress Errors

Fatal error: Uncaught Error: Class "…" not found

“Uncaught Error: Class "…" not found” in WordPress: causes and what to check

Updated 2026-11-01

PHP throws this error when code uses a class that was never loaded. In WordPress, the class usually belongs to a plugin that is inactive, a library an update did not include, or a PHP extension the server does not have. PHP 7 shows the class name in single quotes.

Which of these do you see?

The update changed or removed files, and the autoloader no longer finds the class. An interrupted update leaves the same result.

An add-on calls a class from its main plugin, which is no longer loaded.

Classes such as Redis, Memcached or Imagick come from PHP extensions. When the new server lacks the extension, code that expects it stops.

Common causes

Missing plugin dependency: An add-on is active while the plugin it extends is not.
Incomplete update: Files the autoloader needs were not installed.
Missing PHP extension: The server lacks the extension that provides the class.
File name case: A server that treats file names as case-sensitive cannot find a file whose name differs only by case.

References

  1. Autoloading classes (PHP.net)
  2. Debugging in WordPress (Advanced Administration Handbook)

Rather not fix it yourself? Let WP119 handle it automatically.

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); a white screen caused by exhausted memory is fixed by raising the memory limit. After the fix, the home page and inner pages are re-verified, and only then is the result written back to your host (in WP admin mode, a recovered package is delivered instead). 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: Site URL entry
  2. Copy to the recovery station: Work on a copy
  3. Diagnosis: Item-by-item checks
  4. Recovery and verification: Home and inner pages
  5. Write-back or delivery: Only after verification passes

Use WP119 when this error stops the site or the admin area from loading.

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