How to Identify Which WordPress Plugin or Theme Is Blocking Your PHP Update and Preventing a Smooth Upgrade

If you’ve logged into your WordPress dashboard and seen the warning that your site is running on PHP 7.4.33, you’re not alone. This outdated version no longer receives security updates, which makes your website vulnerable and potentially slower. The recommended PHP version is now 8.3, and updating to it is crucial for both performance and security. But here’s the frustrating part, sometimes when you try to update PHP, your site crashes, and you’re left scrambling to figure out which plugin or theme caused the problem.

Learning how to pinpoint the culprit can save you from downtime and get your site running on the latest PHP without the headaches. Let’s break it down step by step.

Understanding PHP and Its Role in WordPress

PHP is the engine that powers your WordPress site. Every time a visitor lands on your page, PHP is what pulls together your posts, pages, and theme design to deliver a functional website.

Running an outdated PHP version like 7.4.33 exposes you to:

• Security vulnerabilities that hackers can exploit
• Reduced site speed and efficiency
• Incompatibility with newer versions of WordPress, plugins, or themes

When you upgrade to PHP 8.3, you’ll usually get better performance and improved security, but only if your plugins and theme are compatible. If they’re not, you may encounter the dreaded white screen of death, fatal errors, or broken site features after the update.

Step 1: Back Up Your Site Before Anything Else

Before you attempt any PHP updates or plugin checks, create a full site backup. This includes both your website files and the database. You can use:

• Your hosting provider’s backup tool
• A plugin like UpdraftPlus or All-in-One WP Migration
• Manual cPanel backups if you’re comfortable with them

If your site crashes during testing, you can restore it instantly without losing progress.

Step 2: Test Plugin and Theme Compatibility in a Staging Environment

The safest way to identify the problem plugin or theme is by using a staging site. Most web hosts offer a one-click staging feature, or you can use plugins like WP Staging.

Here’s how to approach testing:

1. Clone your live site to the staging environment.
2. Update PHP to 8.3 on the staging site first.
3. Check if the site loads properly.

If your staging site crashes after the update, it confirms that at least one plugin or your theme is incompatible with PHP 8.3.

Step 3: Use the Health Check & Troubleshooting Plugin

WordPress has a free plugin called Health Check & Troubleshooting that can help you identify conflicts without breaking your live site.

• Install and activate the plugin.
• Enable Troubleshooting Mode, which disables all plugins for your user session only (visitors still see the normal site).
• Switch PHP to 8.3 in your hosting panel while troubleshooting mode is on.
• Re-enable plugins one by one until the site breaks or errors appear.

This process quickly reveals which plugin is holding up your PHP upgrade.

Step 4: Check PHP Compatibility with a Scan

Some plugins can check PHP version compatibility without needing a full update trial. Popular options include:

• PHP Compatibility Checker by WP Engine
• Query Monitor for spotting deprecated functions after updates

Run the scan, and it will flag plugins or themes that use outdated PHP functions. While this isn’t always 100% accurate, it provides a strong starting point before manually testing.

Step 5: Narrow Down the Problem Manually if Needed

If you can’t use a staging site or plugin, the old-fashioned method works:

1. Deactivate all plugins and switch to a default theme like Twenty Twenty-Four.
2. Update PHP to 8.3.
3. Reactivate plugins one by one, testing the site after each activation.

The plugin that causes the site to crash or throw errors is the one blocking your update. Sometimes, it’s the active theme instead, especially if it hasn’t been updated in years.

Step 6: Decide on a Fix

Once you’ve identified the incompatible plugin or theme, you have a few options:

• Update it to the latest version if an update is available.
• Replace it with a compatible alternative if the developer no longer supports it.
• Contact the developer and ask about PHP 8.3 compatibility if it’s critical to your site.

In extreme cases where the plugin is essential but unsupported, you may need a developer to modify the code for compatibility or keep your site on a slightly lower PHP version temporarily.

Step 7: Keep Your Site Future-Proof

After successfully upgrading, make it a habit to:

• Regularly update all plugins, themes, and WordPress itself
• Remove outdated or abandoned plugins
• Test major PHP upgrades in a staging environment first

Keeping a lean and well-maintained site reduces the risk of PHP incompatibility and ensures smooth future updates.

Updating to PHP 8.3 isn’t just about following recommendations; it’s about securing your site, speeding it up, and staying compatible with future WordPress releases. By using a combination of staging tests, compatibility scans, and systematic troubleshooting, you can pinpoint the exact plugin or theme that’s holding you back and upgrade without fear of a site-breaking crash.