Table of contents

Common errorsRetrace your stepsActivate error reportingDiagnosing plugin errorsUpgrade your hosting

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Diagnosing WordPress errors on your site

Sometimes, your WordPress site may behave in ways you don’t expect. Perhaps a widget has disappeared from its customary page, or an inscrutable string of numbers are output onto the page, or instead of your WordPress site, all you can see is a blank white page. Usually, the cause of these problems is easily reversible, but before you can fix a problem, you need to know what caused it. Understanding SQL injection attacks can also help you prevent one of the most common security vulnerabilities in WordPress sites.

The usual suspects

If a WordPress site won’t load at all, there may be a problem with your internet connection or – less likely – with your WordPress hosting. If WordPress loads, but it doesn’t look right in some way, the cause is probably one of the following:

Plugin errors or compatibility issues
A missing or damaged theme
Missing or damaged files
Database issues

Plugin compatibility issues are the most common problem and the most likely occur when you haven’t made any obvious changes to your WordPress site’s code.

Retrace your steps

If you are actively working on your WordPress site when the problem arises, perhaps editing a PHP file or installing a plugin, then undo what you just did. It is often useful to maintain a “log” of the changes you are making to a WordPress site, so that when something goes wrong you know exactly what you need to do to backtrack until you find the mistake.

Activate error reporting

By default, WordPress doesn’t report errors to the display for security reasons, but you can activate error reporting by SSHing into your account, opening wp-config.php, and editing the following configuration option.

define( 'WP_DEBUG', false );

Change false to true so that the line reads:

define( 'WP_DEBUG', true );

This will make WordPress report errors that may be useful in tracking down the cause of the problem. Don’t forget to revert to the default when you have found the problem.

Diagnosing plugin errors

Incompatible and otherwise faulty plugins are the most common cause of errors on WordPress sites. If you haven’t recently made any significant changes to your site, plugins should be at the top of your list of suspects.

But which plugin is causing the problem? There are two ways to manually figure out which plugin is misbehaving. The first is to disable plugins one at a time until the problem goes away. The second is to disable all plugins, and reactivate them one-by-one until the problem returns.

Occasionally, the problem is so bad that you can’t access the admin interface to deactivate plugins — the so-called White Screen of Death. The solution is to manually deactivate all plugins by logging in to your hosting account by FTP or SSH and renaming the wp-content/plugins folder to something different: the WordPress Codex recommends wp-content/plugins-old.

For sites with many plugins, it takes a lot of reactivating and deactivating to discover which plugin is causing the problem, especially if it’s caused by the interaction of a couple of plugins. Plugin Detective can help. It’s a WordPress plugin that leads you through a binary search of installed plugins, narrowing down the culprit more quickly and reliably than doing the same thing manually.

This article should help you quickly diagnose and fix the most common issues you might have with your WordPress site, but if you need more help, don’t hesitate to get in touch with Liquid Web support.

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