How to fix Warning: Undefined property in wordpress?

Error:

Warning: Undefined property: stdClass::$plugin in /home/badshaht/domainurl/wp-includes/class-wp-list-util.php on line 167

The warning message Warning: Undefined property: stdClass::$plugin in /home/badshaht/domainurl/wp-includes/class-wp-list-util.php on line 167, is indicative of a PHP issue in your WordPress environment. This type of warning usually occurs due to one of the following reasons:

1. Plugin or Theme Conflict: The most common cause of this warning is a conflict between plugins or between a plugin and your current theme. It could be that a plugin is trying to access a property ($plugin) on an object that doesn’t exist or hasn’t been properly defined.
2. Outdated Plugins or Theme: If a plugin or your theme is outdated, it might not be compatible with the current version of WordPress you are using, leading to such warnings.
3. Corrupted Files: Occasionally, WordPress files can become corrupted, either due to a failed update, issues during file transfer, or server problems.

Here’s what you can do to troubleshoot and potentially resolve the issue:

Debugging Steps

1. Update Everything: Ensure that all your plugins, themes, and the WordPress core are updated to their latest versions.
2. Deactivate Plugins: Try deactivating all your plugins. If the warning goes away, reactivate them one by one to identify the culprit. This is a common method for isolating problematic plugins.
3. Switch Themes: Temporarily switch to a default WordPress theme like Twenty Twenty-One. If this resolves the issue, the problem might be with your theme.
4. Check Error Logs: Look into the WordPress and server error logs for more detailed information about this warning. This might give you clues about which plugin or theme function is causing the issue.
5. WordPress Debug Mode: Enable WordPress debug mode by setting define('WP_DEBUG', true); in your wp-config.php file. This might provide more detailed error messages. Remember to turn this off after debugging as it’s not recommended for live sites.
6. Consult with the Plugin/Theme Developer: If you pinpoint the issue to a specific plugin or theme, reaching out to the developer for support can be very helpful.
7. Restore from Backup: If you recently made changes to your site, consider restoring from a backup taken before the changes.
8. Server Environment: In rare cases, server configuration issues can cause this problem. You might want to consult with your hosting provider.

A Note on PHP Warnings

This warning is a non-fatal error, meaning it doesn’t stop the execution of the script. However, it’s important to address it to ensure your site functions correctly and to prevent potential security vulnerabilities. If you’re not comfortable performing these steps yourself, consider getting help from a professional WordPress developer.