__autoload() no longer supported after a PHP update

What the message means

The message __autoload() is no longer supported identifies a legacy mechanism for loading PHPPHP is a programming language that builds your web pages on the computer that hosts your site, just before they reach the visitor. WordPress runs on it. classes. A class groups code belonging to a component. PHP 8 removed support for this special function.

Its migration guide points to spl_autoload_register(). This article concerns that removed loading mechanism, rather than every possible class-not-found error.

Before changing anything

Keep the complete error line and its timestamp in a private note. Record the action that failed, the active PHP versionA PHP version is a numbered edition of PHP, like 8.3. Each edition is looked after for a limited time, then gets security fixes only, then nothing. and the components updated at the same time. Share only information needed for the investigation.

Public support forums are not an appropriate place for customer details, credentials or complete server paths.

Back up files and the database before making changes. Check that the backupA backup is a separate copy of your website's files and database, so you can bring the site back after a mistake, a hack or a failed update. is usable. Work on a private test copy with the same PHP version and relevant settings.

Disable real payments and outgoing customer email there. Agree who will make the change and who will check the outcome. The steps below are investigation advice rather than a diagnosis of your particular website.

Possible cause

Locate the definition of __autoload in the reported file. Check whether a pluginA WordPress plugin is an add-on you install in WordPress to give your site extra features, such as contact forms, SEO tools or a webshop., themeA WordPress theme is a ready-made package that decides how your WordPress site looks and how its pages are laid out. Change the theme and the design changes. or bundled library owns it. A PHP update can expose old loading code, but does not establish which package needs repair.

Identify the maintainer before editing. Renaming the function alone does not register the replacement as a class loader.

Fix it in five steps

1. Record the file containing the old function and the package that supplies it. Keep the package version so its maintainer can inspect the same implementation.
2. Check for a suitable supplier update. For custom code, ask which classes the loader must find and where their files should be located.
3. Have the replacement registered through spl_autoload_register(). Ask how it cooperates with existing loaders rather than replacing the whole loading sequence without investigating it.
4. Test the first use of the affected class in a fresh request. Loading a screen that never uses that class does not demonstrate a successful repair.
5. Check both the visitor journey and the administration action using the package. Record the class loaded and inspect fresh logs for the original message.

A concrete acceptance test

A WordPress plugin displaying a document preview provides a useful proposed test. Open its preview and settings screen on the test copy. Agree which document and settings should appear before testing.

Repeat from a fresh session. This example does not identify a defective real plugin. If a class-not-found message follows, ask the developer to investigate its path and registration instead of loading additional files at random.

Record the actual document result as well as whether the page opens.

Identify who maintains the code

For a plugin or theme, first ask which release fits the intended PHP environment. Give its maintainer the error line and the action that reproduces it. Request a focused change with an explanation of the expected result.

The same explanation belongs in a handover to the developer of custom code.

Avoid changing unrelated components during the same investigation. Keep the original message separate from any new messages after an adjustment. Record the code version and test inputs for each attempt.

This lets you associate a result with a specific change. A test where nobody knows which files changed cannot provide useful acceptance evidence.

Agree in advance what would make the test fail. Examples include incorrect content, lost settings or a visitor action that can no longer be completed. Making a warning disappear is only part of the check.

Ask the website owner to assess the result that a visitor actually needs, alongside the technical review of the change.

When to get help

Use the existing PHP update service or the help form below if you cannot access the code or do not maintain the affected library. Describe the failed action and intended outcome. Do not send passwords.

Ask which correction is proposed and which test will establish that it works.

Use the Exposure Check through the Check your PHP version link as an initial version check. A public check cannot always determine the PHP version and does not prove the cause or repair of this error. If the result is unknown, ask the host to confirm the active version for this website.

After repair, keep versions, test results and fresh log entries with your maintenance notes. Let the responsible administrator decide when the tested change can reach the live website.

At handover, ask which test deliberately exercises an incorrect class name. This helps distinguish a working registration from a file that happened to be loaded already. Have the developer explain the outcome before accepting the change as complete.