WordPressの重大なエラー：原因と解決策

If you’ve ever opened your ワードプレス website and been greeted by a message saying “There has been a critical error on this website”, you’re not alone.

The WordPress critical error is one of the most confusing and stressful problems site owners face—especially for non-technical users, business owners, or cross-border sellers who rely on their website for traffic and revenue.

This article explains the WordPress critical error in plain English.
We’ll cover what it is, why it happens, how to fix it safely, and—most importantly—how to prevent it from happening again.

No unnecessary jargon. Just clear explanations and practical guidance.

WordPress の重大なエラーとは何ですか?

A WordPress critical error occurs when WordPress encounters a fatal PHP error that prevents the website from loading properly.

Instead of displaying broken layouts or partial content, WordPress stops execution entirely to avoid further damage. That’s why visitors may see:

• A white screen
• A generic “critical error” message
• Or no visible content at all

Since WordPress 5.2, the platform includes a built-in fatal error protection system, which replaces the old “white screen of death” with a clearer message and sometimes an admin recovery email.

WordPressが「重大なエラー」メッセージを表示する理由

At its core, WordPress is powered by PHP.
When PHP code fails in a way that WordPress cannot safely recover from, a critical error is triggered.

These errors typically come from customizations, plugins, or themes, not WordPress core itself.

WordPressの重大なエラーの最も一般的な原因

Let’s break down the most frequent reasons this issue appears.

1. Plugin Conflicts or Bugs

Plugins are the #1 cause of WordPress critical errors.

This often happens when:

• A plugin update introduces incompatible code
• 2つのプラグインが競合しています
• A plugin is not compatible with your PHP version
• A plugin uses deprecated WordPress functions

Page builders, performance plugins, security plugins, and e-commerce extensions are especially common triggers.

2. Theme Issues and Theme Updates

Themes can also cause fatal errors, especially when:

• A theme update removes or changes required functions
• Custom code is added incorrectly to 関数.php
• A child theme is missing dependencies

If your site crashes right after changing or updating a theme, this is a strong signal.

3. PHPバージョンの非互換性

Your hosting server runs a specific PHP version.

If:

• PHP is updated automatically by the host
• Your plugins or theme don’t support the new version

WordPress may fail instantly.

Many older plugins still rely on outdated PHP syntax, which modern PHP versions reject.

4. メモリ制限の枯渇

WordPress requires memory to run scripts.

A critical error may occur if:

• Too many plugins load at once
• A heavy page builder runs complex layouts
• WooCommerce processes large queries

When PHP memory is exhausted, execution stops.

5. Corrupted Core Files or Incomplete Updates

Interrupted updates can leave WordPress in an unstable state.

This can happen due to:

• Server timeouts
• Connection drops
• Insufficient file permissions

As a result, essential core files may be missing or corrupted.

6. Incorrect Custom Code

Adding code manually—whether in a theme file, custom plugin, or snippet manager—can easily cause fatal errors if syntax is incorrect.

Even a missing semicolon can break the entire site.

How WordPress Helps You Recover from Critical Errors

Modern WordPress includes a recovery mode.

When a critical error occurs:

• WordPress sends an email to the site admin
• The email includes a secure recovery link
• This link allows you to log in and disable the problematic plugin or theme

This feature has made troubleshooting significantly easier compared to older versions.

ステップバイステップ：WordPressの重大なエラーを修正する方法

Here’s a safe, structured approach.

ステップ1: 回復メールを確認する

Always start by checking your admin email inbox.

If WordPress detected the issue, it will tell you:

• Which plugin or theme caused the error
• How to access recovery mode

This is often the fastest fix.

Step 2: Disable All Plugins (If Needed)

If you can’t access wp-admin:

1. Log in to your hosting file manager or FTP
2. Navigate to /wp-content/
3. 名前を変更する プラグイン folder (e.g., プラグイン_old)

これにより、すべてのプラグインが一度に無効になります。.

If the site loads, the issue is plugin-related.

Step 3: Reactivate Plugins One by One

フォルダ名を元に戻します プラグイン, then:

• Activate plugins individually
• Refresh the site after each activation

When the error returns, you’ve found the culprit.

ステップ4: デフォルトのテーマに切り替える

If plugins aren’t the issue:

• アクティブなテーマフォルダの名前を変更する
• WordPressは自動的にデフォルトのテーマに戻ります

If the site works again, the theme is responsible.

Step 5: Check PHP Version Compatibility

Inside your hosting panel:

• Try switching to a different PHP version
• Test commonly supported versions like PHP 8.0 or 7.4

Many WordPress environments stabilize immediately after this change.

Step 6: Increase PHP Memory Limit

Low memory is a silent killer.

編集することでメモリを増やすことができます wp-config.php:

'WP_MEMORY_LIMIT'、'256M'を定義します。;

This helps with complex sites and page builders.

Step 7: Enable Debug Mode for Deeper Insight

For persistent issues, enable debugging:

define(‘WP_DEBUG’, true);
define(‘WP_DEBUG_LOG’, true);
define(‘WP_DEBUG_DISPLAY’, false);

Then review the error logs to identify exact causes.

How to Prevent WordPress Critical Errors Long-Term

Fixing the issue is one thing. Preventing it is what really matters.

1. Use Quality Plugins Only

避ける：

• 放棄されたプラグイン
• Poorly reviewed tools
• Plugins updated years ago

Stick to actively maintained, well-supported plugins.

2. Always Test Updates

Never update directly on a live business website.

使用：

• Staging environments
• Backup snapshots

This is especially important for cross-border e-commerce sites.

3. Keep PHP, WordPress, and Plugins Aligned

Compatibility matters more than “latest version”.

A stable setup beats a bleeding-edge one.

4. Avoid Random Code Snippets

Copy-pasting code from forums without understanding it is risky.

One bad snippet can cause a full site outage.

5. Choose Professional Hosting

Cheap hosting often lacks:

• Proper PHP controls
• Error logging
• Rollback tools

Reliable infrastructure dramatically reduces fatal errors.

Why WordPress Critical Errors Are Especially Dangerous for Cross-Border Businesses

For international sellers, a broken website doesn’t just mean downtime.

It can mean:

• Lost ad traffic
• Broken payment flows
• SEO ranking drops
• Damaged brand trust

That’s why technical stability and structured design are not optional—they’re business foundations.

Final Thoughts: Don’t Just Fix Errors—Build Stable Systems

A WordPress critical error is rarely “random”.

It’s usually a sign of:

• Poor plugin architecture
• Unplanned updates
• Lack of technical oversight

With the right structure, most critical errors are completely avoidable.

AIRSANGについて

で エアサン, we specialize in cross-border websites built for stability, scalability, and long-term growth.

From ワードプレス site architecture and performance optimization
to e-commerce design and international business workflows,
we help brands avoid problems like WordPress critical errors before they happen.

If your website is critical to your business—and especially if you operate globally—
エアサン is here to help you build it right from the start.