Fixing the 'Uncaught TypeError: Argument 3 passed to Redux_Extension_Customizer' Error in WordPress

If you're encountering a fatal PHP error when trying to access the WordPress Customizer (Appearance > Customize) that mentions Redux_Extension_Customizer::add_section(), you're not alone. This is a common issue reported by users of the Redux Framework plugin. This guide will explain why this error occurs and walk you through the most effective solutions to resolve it.

Understanding the Error

The error message typically looks like this:

Uncaught TypeError: Argument 3 passed to Redux_Extension_Customizer::add_section() must be an instance of object, instance of WP_Customize_Manager given...

This is a PHP type error that indicates a code incompatibility. It often arises from a mismatch between the version of the Redux Framework plugin you are using and the version of PHP running on your server. The code expects one type of object but is receiving another, which is a common symptom of code written for a newer version of PHP (7.0+) running on an older, unsupported version (e.g., PHP 5.6).

How to Fix the Redux Customizer Error

Follow these troubleshooting steps to identify and resolve the cause of the problem.

Solution 1: Update Your PHP Version (Most Common Fix)

The most likely cause of this error is an outdated PHP version. Redux Framework, like most modern WordPress plugins, is developed and tested on current, supported versions of PHP.

1. Check your current PHP version. You can often find this in your WordPress admin dashboard under Tools > Site Health > Info > Server, or in your hosting control panel (e.g., cPanel).
2. If your server is running a version of PHP older than 7.4, you need to update it. The Redux Framework team recommends using PHP 7.4 or higher for compatibility and security.
3. Contact your web hosting provider for assistance in upgrading your PHP version. Most hosts make this very simple through their control panel.

Solution 2: Perform a Conflict Test

If updating PHP does not resolve the issue, or if you are already on a supported version, a plugin or theme conflict may be the cause.

1. Switch to a default theme: Temporarily change your theme to a WordPress default theme like Twenty Twenty-Three or Twenty Twenty-Four. Does the error disappear? If yes, the issue is with your theme's implementation of Redux, and you should contact the theme author for support.
2. Disable all plugins: If the error persists with a default theme, deactivate all your plugins except Redux Framework.
3. Check the Customizer: See if the error is now gone.
4. Re-enable plugins one by one: Reactivate your plugins one at a time, checking the Customizer after each activation. This process will help you identify which plugin is causing the conflict.

Solution 3: Ensure Redux is Updated and Properly Installed

Ensure you are using the latest stable version of the Redux Framework plugin. An outdated or corrupted installation can sometimes cause unexpected errors.

1. Go to Plugins > Installed Plugins in your WordPress admin.
2. Check if an update is available for Redux Framework and apply it.
3. If problems continue, try a clean reinstall: deactivate and delete the Redux Framework plugin, then install it fresh from the WordPress plugin repository.

Conclusion

The 'Uncaught TypeError' in the Redux Customizer is almost always solved by upgrading the site's PHP version to 7.4 or higher. If the error continues after that, a systematic conflict test is the best way to identify an incompatible theme or plugin. Remember, if the problem is traced back to your theme, you will need to reach out to the theme's developer for further assistance, as they are responsible for their own implementation of Redux Framework.