Fix MediaWiki Internal Errors When Editing Pages

MediaWiki internal errors during page editing are frustrating, often caused by server misconfigurations, extension conflicts, or file permission issues. This guide walks you through diagnosing and fixing the most common causes, from clearing caches to adjusting PHP settings, so you can get back to editing smoothly.

What You’ll Need

• Administrative (shell) access to your MediaWiki server, or at least the ability to edit PHP files and run maintenance scripts.
• FTP/SFTP or a file manager to access the MediaWiki installation directory.
• Access to your server’s error logs (e.g., via cPanel, Plesk, or command line).
• Basic knowledge of PHP and server configuration.

Step-by-Step

1. Check the server error log. The most direct way to find the root cause is to look at the PHP error log or the web server’s error log (Apache, Nginx). Look for entries that occur at the exact time you tried to edit a page. The error message will often point to a specific file and line number.
2. Clear MediaWiki caches. Sometimes stale cached data causes errors. Run the maintenance script to purge all caches:
   php maintenance/runJobs.php and then php maintenance/rebuildrecentchanges.php (optional). Also, delete the /cache directory contents (keep the directory itself).
3. Check file permissions. MediaWiki needs to write to the images directory and sometimes the cache directory. Ensure that the web server user (e.g., www-data) has write permissions to these directories. Incorrect permissions can cause internal errors when trying to upload or save edits. Use chmod -R 755 images and chown -R www-data:www-data images (adjust to your user/group).
4. Disable extensions temporarily. If the error started after installing or updating an extension, disable it by renaming the LocalSettings.php entry or moving the extension folder. Edit LocalSettings.php and comment out the wfLoadExtension() lines one by one, testing after each. If the error disappears, the last disabled extension is the culprit.
5. Check PHP memory limit. Editing large pages can exhaust PHP memory. Increase the memory limit in LocalSettings.php by adding:
   ini_set( 'memory_limit', '256M' );
   If that doesn’t help, check your PHP configuration (php.ini) and increase memory_limit globally.
6. Verify PHP version compatibility. MediaWiki requires a specific PHP version. Check the RELEASE-NOTES file in your MediaWiki installation for the required PHP version. If you’re using an outdated PHP version, upgrade it or downgrade MediaWiki to a compatible version.
7. Check for database issues. Run the database maintenance script:
   php maintenance/update.php
   This will apply any pending schema updates. If the database is corrupted, you may need to restore from a backup.
8. Check for syntax errors in LocalSettings.php. A missing semicolon or a bad line in LocalSettings.php can cause internal errors. Run php -l LocalSettings.php to check for syntax errors.
9. Disable object caching. If you’re using a caching system like Memcached or Redis, try disabling it temporarily by setting $wgMainCacheType = CACHE_NONE; in LocalSettings.php. This can help isolate caching-related issues.
10. Check for .htaccess or Nginx configuration issues. If you have custom rewrite rules, they might interfere with page editing. Temporarily rename .htaccess (Apache) or comment out custom Nginx location blocks to see if the error resolves.

Common Mistakes

• Ignoring the error log. Trying random fixes without checking the log wastes time.
• Changing file permissions too broadly. Setting chmod -R 777 can create security risks. Use the least permissive settings that work.
• Disabling all extensions at once. This makes it hard to identify which one is causing the problem.
• Not clearing the cache after changes. Even after fixing the root cause, you may still see the error if the cache isn’t cleared.
• Editing LocalSettings.php without a backup. Always back up the file before making changes.

Tips

• Enable $wgShowExceptionDetails = true; in LocalSettings.php to see detailed error messages on the page. This is invaluable for debugging.
• Use a test environment (a local copy of your wiki) to try fixes before applying them to production.
• Keep MediaWiki and all extensions up to date. Many internal errors are fixed in newer versions.
• If you’re using a shared host, contact your hosting provider for help with server-level settings like PHP memory limits.

Troubleshooting

If the steps above don’t resolve the issue, try these additional checks:

• Check for conflicts with other software. If you have a firewall or security module (like ModSecurity), it might be blocking POST requests to the edit page. Temporarily disable it to test.
• Look for custom skins or templates. If you’re using a custom skin, it might have PHP errors. Switch to the default Vector skin to see if the problem persists.
• Check the PHP error log again after each step. The error message may change, giving you more clues.
• If the error is specific to one page, try editing a different page. If the error only occurs on that page, the page content might be corrupted. Use the maintenance/rebuildall.php script to rebuild the page cache.
• If all else fails, consider reinstalling MediaWiki (keeping your database) or restoring from a backup.

Frequently Asked Questions

Why do I get an internal error only when editing, not when viewing?

Editing involves more complex operations (saving to the database, updating caches, rendering diffs) that can trigger memory limits, extension hooks, or file write issues that aren’t hit during simple page views.

How do I find the exact error message?

Enable $wgShowExceptionDetails = true; in LocalSettings.php. This will display the full error trace on the page. Also check the PHP error log (often in /var/log/php_errors.log or similar).

Can a corrupted database cause internal errors?

Yes, if the database tables are corrupted, especially the page or revision tables, editing can fail. Run php maintenance/update.php to repair schema issues, or use database repair tools like mysqlcheck.

What if I can’t access the shell?

If you’re on shared hosting without shell access, you can still edit LocalSettings.php via FTP. You can also add the debug lines to a PHP file and upload it. For cache clearing, you can delete the /cache folder contents via FTP.

Do I need to clear the browser cache?

Sometimes, but internal errors are server-side. However, after fixing the issue, clearing your browser cache can help if you’re seeing a cached error page.

Is it safe to increase PHP memory limit?

Yes, increasing the memory limit to 256M or 512M is generally safe for MediaWiki. However, if you’re on shared hosting, the host may have a hard limit. Contact them if you exceed it.

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