How to Fix Fatal Error: Call to Undefined Function WordPress

Installing a new plugin for added features just triggered the fatal error: call to undefined function WordPress. Or maybe a recent theme update logged you out of your admin dashboard, leading to the same issue.

We know, how frustrating it is as a site admin. You only wanted to perform maintenance tasks, but now you’re stuck troubleshooting. 

But don’t worry. This guide offers straightforward steps to quickly fix the problem in minutes and get everything back on track.

TL;DR: The fatal error: call to undefined function WordPress message occurs when your site attempts to use a missing function, potentially leading to site malfunctions. To prevent data loss during troubleshooting, ensure you have a reliable backup of your site.

Understanding the error

The fatal error: call to undefined function WordPress error occurs when your site attempts to use a missing piece of function. 

Functions are crucial for various tasks on your WordPress site. If one is absent, the site can malfunction. How does it affect your site? This error might result in a blank homepage or an error message with confusing details. In severe cases, your site may become entirely inaccessible.

Common causes

Plugin issues: Often, a problematic plugin can conflict with your theme or disrupt other functions after an update, leading to this error.

Missing WordPress files: Sometimes, core WordPress files may get damaged or removed, causing essential functions to go missing.

Faulty custom code: Even minor errors in custom code, such as a missing comma, can lead to significant issues on your site.

Hosting problems: Your web host might be using outdated software that is incompatible with the latest WordPress versions, resulting in function-related errors.

File damage: Files may become corrupted due to failed uploads, server issues, or malware, which can affect their ability to function correctly.

Fixing the fatal error: call to undefined function WordPress

Running into the fatal error: call to undefined function WordPress message on your site is frustrating. But, with these steps, you’ll have your site back up and running smoothly in no time. Here’s how to go about it:

1. Reinstall your WordPress core files

Sometimes, the building blocks of your WordPress site, known as core files, go missing or get damaged. Here’s how to fix it:

Head over to WordPress.org and download the latest version of WordPress

Use FTP to connect to your website’s files. Your hosting provider will have login details for you

Upload the new WordPress files to your site, but make sure you skip the wp-content folder so you don’t lose your themes and plugins

When it asks if you want to replace existing files, click on Yes. This will replace any corrupted files with fresh ones. Once done, double-check to ensure all the file permissions are set correctly.

2. Look for typos in code

Even the tiniest typo in your code can cause big problems:

Look at recent changes you made to your functions.php file or any custom code. Carefully check for any misspelled words or wrong punctuation marks. If you find any errors, fix them. Next, save your changes and refresh your site to see if it’s working now.

3. Deactivate plugins

Plugins are like apps for your website, and sometimes they don’t play nice. Here’s what to do:

• If you can get into your WordPress dashboard, navigate to the Plugins section
• Disable all your plugins and then turn them back on one by one. This will help you find the one causing trouble

• If you can’t access your dashboard, don’t panic. Connect to your site using FTP
• Go to the wp-content/plugins folder and rename each plugin folder by adding .deactivate at the end. This will deactivate them temporarily until you change it back

• Rename them back one by one, and keep an eye on your site until you find the plugin that’s causing the mess.

4. Revert to a default theme

Sometimes, the theme you’re using might be the issue. Let’s try using a basic, default theme:

• If you can, log into your WordPress dashboard and go to Appearance > Themes.
• Activate a simple theme like Twenty Twenty-Four.

• If you can’t get into your dashboard, connect via FTP and rename your current theme folder. This will automatically switch your site to a default theme. Once done, check to see if the error is still there.

5. Update PHP version

WordPress and PHP need to get along, and using an old PHP version can cause problems. Here’s how to update it:

Find out your current PHP version through your hosting control panel or WordPress site. Update to a recommended PHP version, ideally PHP 7.4 or higher.

Once updated, take a stroll through your site to ensure everything is working perfectly.

Best practices to avoid this error

To keep your WordPress site running smoothly and avoid future errors, follow these simple steps:

Keep WordPress updated: Regularly install the latest WordPress version to ensure your site is up-to-date with all the new features and fixes.

Update plugins and themes: Always update plugins and themes to their latest versions to maintain your site’s functionality and security.

Use a reliable backup solution: Regularly backup your site to safeguard your data and quickly restore it if something goes wrong.

Choose plugins and themes wisely: Download plugins and themes only from reputable sources to avoid potential problems.

Double-check custom code: Carefully review and test them on a staging site any custom code to prevent errors from occurring.

Minimize plugins: Limit the number of plugins to reduce the risk of conflicts that can lead to errors.

Stay compatible with PHP: Ensure your server runs a PHP version that’s compatible with WordPress for optimal performance.

Use security plugins: Install a security plugin to regularly scan for and remove malware, keeping your site safe.

Final thoughts

Understanding what causes the fatal error: call to undefined function WordPress message allows you to swiftly address and resolve the issue, minimizing any downtime and disruption. 

By taking quick action and regularly maintaining and updating your site, you can prevent future errors from occurring. 

Always trusting reliable resources enhances your site’s security and stability, while adopting best practices ensures a smoother and more efficient WordPress experience. 

FAQs

How do I fix a fatal error in WordPress?

To fix a fatal error, identify the source by checking recent changes like updates or code edits. Disable plugins or themes, and restore or reinstall any corrupted core files. Always backup your site before making changes.

What is “call to undefined function” in WordPress?

The call to undefined function error means that WordPress is trying to use a function that doesn’t exist. It can be due to missing files or code errors, often from plugin issues or incorrect theme modifications.

How to access site files?

You can access site files via FTP using software like FileZilla, or through your hosting provider’s file manager. Use the login details provided by your host to connect to your site’s root directory.

How do I debug a WordPress error?

Enable WordPress debugging by adding define(‘WP_DEBUG’, true); to your wp-config.php file. This displays error messages that can help pinpoint the issue. Always turn off debugging on live sites after resolving the error.

What is the memory limit for WordPress?

The default memory limit for WordPress is typically 32 MB. You can increase it by editing the wp-config.php file, adding define(‘WP_MEMORY_LIMIT’, ‘256M’); to handle larger demands.