Diagnosing Critical Errors in WordPress: A Survival Guide

Knowledgebase Article

Diagnosing Critical Errors in WordPress: A Survival Guide

So, you woke up, stretched, grabbed your coffee, and went to check your website—only to be greeted by the digital equivalent of a brick wall: the dreaded "There has been a critical error on this website."

Nice.

Don't panic! Your site isn't gone forever, but we need to do some detective work to bring it back to life. Let’s walk through how to diagnose and fix critical errors in WordPress, step by step.

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Step 1: The Error Log—Your Digital Crime Scene

If your WordPress site has crashed, the first place to investigate is the PHP error log. This is like a security camera footage of what happened just before your site decided to take a nap.

Where Do You Find This Mystical Log?

If you're using cPanel: Navigate to File Manager > Open your public_html folder (or the root folder for an addon domain/subdomain). Look for a file named error_log. If the file is very large, viewing it in cPanel might be difficult, and using SSH is recommended.
Over SSH (for the cool kids): Run this command while inside the site's directory:

tail -n 50 error_log

This shows the last 50 lines of the error log, which is useful because the most recent errors appear at the end. If the log is extremely large, it likely indicates recurring issues.

Another handy option is:

less error_log

This allows you to scroll through the file, but for very long logs, it can be trickier to navigate. To exit less, simply press q on your keyboard.
Ninja Move: If you need a bigger snippet but don’t want to load the entire file, try:

tail -n 200 error_log | less

This uses tail to load the last 200 lines into less, giving you more context while keeping it manageable.

Step 2: Who (or What) is the Culprit?

Once you've opened the error log, it’s time to figure out what actually happened. Look for error messages that mention things like:

A specific plugin (e.g., plugins/cool-plugin/cool-plugin.php on line 87)
A theme issue (e.g., themes/fancy-theme/functions.php)
A PHP version mismatch (e.g., Fatal error: Uncaught Error: Call to undefined function xyz_function()—this often means your PHP version is too old or too new for the plugin/theme to handle.)

The key here is to identify what was being called just before the site crashed. If the error log points to a plugin or theme file, that’s a strong indicator of where the issue lies.

Step 3: "But I Didn’t Change Anything!"

Ah, the classic line. Many website owners swear up and down that they didn’t touch a thing before their site imploded.

Here’s the secret: WordPress can break itself.

This happens because plugins and themes can be set to auto-update. Even if you didn’t log in and update anything, a plugin might have upgraded itself overnight, introducing a compatibility issue that crashed the site.

Checking Auto-Update Status:

Even if you can’t access your WP dashboard, you can use WP Toolkit in cPanel to verify which plugins/themes have auto-updates enabled:

Open cPanel
Navigate to WP Toolkit
Select your WordPress site
Click on Plugins or Themes and look for the auto-update status.

If a plugin or theme updated just before the crash, you’ve likely found the culprit.

Step 4: Disabling the Suspect Plugin

If your error log reveals that a specific plugin is responsible for the crash, the next move is to disable it without logging into WordPress (since, you know, your site is currently down).

Open WP Toolkit in cPanel
Select your website
Click on Plugins
Find the suspect plugin and disable it

Step 5: Restoring Order

Disabling the problematic plugin got your site back, but now what?

If WordPress Core is outdated → Update it in WP Toolkit.
If your theme is outdated → Update it via WP Toolkit or manually.
If PHP is the issue → You may need to change PHP versions. Here’s how.
If the plugin is the issue → Check if an update is available or replace it with an alternative.

Step 6: When All Else Fails—Restore from Backup

If your site is still down, restoring from a backup might be necessary—but let’s not go nuclear just yet. A full account restore is rarely a good idea, unless you fancy restoring every single email, every website on your account, and probably your hopes and dreams along with it. Instead, let’s take a more surgical approach:

Use JetBackup to selectively restore the affected plugin or files.
Check if you have a WP Toolkit backup
If you use a backup plugin, see if you can restore from there.
If you're unsure, contact our support team—we can help diagnose and restore only what’s necessary, rather than rolling the whole thing back to the digital Stone Age.

Oh, and if the issue was caused by auto-updates, you might want to turn those off (at least for the problematic plugin). Otherwise, you’ll be back here tomorrow with the same problem, wondering why you didn’t listen to your past self.

Step 7: Avoiding Future Catastrophes

If you must enable auto-updates, consider using Smart Updates instead. This service runs a test update in a staging environment first, so you can verify everything works before rolling it out live.

Here’s a guide on Using Smart Updates in WP Toolkit.

Step 8: Still Stuck? We’ve Got Your Back

If you’ve tried everything and your site is still down, our team is here to help. Sometimes diagnosing these errors requires an extra set of eyes (and a strong cup of coffee).

Open a ticket in MyKualo and we’ll get your site back up and running.

WordPress critical errors can be scary, but once you know where to look, fixing them is like solving a mystery. With a bit of log-reading, detective work, and some smart preventive measures, you can keep your site running smoothly.