White screen after a PHP upgrade? How to fix and roll back

Why does your site go white after a PHP upgrade?

Usually because an old plugin or theme throws an error on the new PHP. When WordPress hits a fatal error like that, it shows a blank page or a short message such as "There has been a critical error on this website."^1·2

Both PHP errors and database errors can manifest as a white screen, a blank screen with no information. — WordPress.org, Common WordPress Errors, updated Oct 14, 2026

When you move into a new house, sometimes one old piece of furniture won't fit through the door. Nothing's wrong with the house, and the furniture isn't broken. The two just don't match. The same thing happens between a plugin (an add-on that gives WordPress extra features) and a new version of PHP. Kinsta says this kind of error "can usually be traced back to an issue with PHP," and that when a PHP update causes trouble, the culprit is "almost always a plugin or an active theme."^3·4

1. First aid: switch PHP back to the old version for now, to get the site back
2. Find the cause: use the debug log (debug.log) to see which file failed
3. Switch it off: turn off or replace that plugin or theme
4. Fix it: update it to the latest version or swap in a different plugin
5. Upgrade again: go back to the new PHP and check your pages and forms

Step 1 only buys time. You're not done until step 5. This guide is as of October 25, 2026, and based on WordPress's own documentation and major hosts' help pages.

Don't stop at step 1.

Jeensuk's takeA white screen doesn't mean your site disappeared. It means it isn't showing you the error message. The culprit is usually a single plugin.

How do you get the site back first?

In your hosting dashboard, switch the PHP version back to the old one for now.

When someone's hurt, you stop the bleeding first and go to the hospital second. Rolling back is stopping the bleeding. Get the page your customers see working again, then look for the cause.

Most hosts let you change the PHP version from the dashboard. At Hostinger, for example, you go to Websites → Dashboard → PHP Configuration, pick a version and click Update, and it changes "within a couple of minutes."⁵

A rollback is first aid. If the old version no longer gets security fixes, your site is at risk again for as long as you stay on it.

Jeensuk's takeOnce the site is back, aim to fix the cause and return to the new version the same day. You don't leave a tourniquet on for long.

How do you find which plugin is causing it?

Turn on WordPress's debug log, and it records the file that caused the error.

A white screen is like a patient who won't talk. The debug log is the patient's chart. It can't say where it hurts, but it's in the record. WordPress's documentation says to add these three lines to the settings file wp-config.php, before the line that reads "That's all, stop editing!"⁶

Switch to the new PHP version again to trigger the problem, then open debug.log in the wp-content folder. You'll see the path of the file that failed. If the path contains /plugins/plugin-name/, that plugin is the cause. If it contains /themes/theme-name/, it's the theme (the design package that controls how your site looks).

When you're done, take the three lines back out and delete debug.log. WordPress says not to use its debug tools on live sites,⁶ and the hosting platform SpinupWP warns that in the default location, "anyone can view your error logs simply by visiting the log file's URL."⁷ You don't leave a medical chart on the sidewalk.

Jeensuk's takeSetting WP_DEBUG_DISPLAY to false is the important part. It keeps errors in the log file instead of on the page your customers see.

How do you switch it off if you can't get into the dashboard?

Rename folders using FTP or SFTP (a way to move files to and from your server) or your host's file manager. Here's the order WordPress and Kinsta describe.^1·3

When the power's out, you can flip every breaker off and then turn them back on one by one to find the room with the short. Finding the bad plugin works the same way.

1. Turn off every plugin: rename the wp-content/plugins folder to something like plugins_old. Kinsta: "Rename the plugins folder to plugins_old and verify that your site is working again." If the site comes back, a plugin is the cause.³
2. Turn them on one at a time: rename the folder back to plugins, then activate plugins one by one until the screen goes white again.^1·3
3. Check the theme: rename your active theme's folder in wp-content/themes. WordPress falls back to a default theme (such as Twenty Twenty-One) if one is installed. If the site comes back, the theme is the cause.¹
4. Use the recovery email: since WordPress 5.2, a fatal error can trigger an email to your site's admin address with a special "recovery mode" link. Through that link, the plugin or theme causing the error is paused so you can get into the dashboard and deal with it.²
5. Raise the memory limit: if the problem is running out of memory, Kinsta suggests define( 'WP_MEMORY_LIMIT', '128M' );, and 256M if that isn't enough.³

Jeensuk's takeYou're only renaming folders, not deleting files. Still, take a backup before you start.

Once you've found the cause, how do you finish?

Update the plugin to its latest version or replace it with a different one, then move up to the new PHP version again.

Finally, check your pages, your contact form and the Site Health screen. If you can reach your server over SSH (a way to log in and run commands remotely), WP-CLI's wp core verify-checksums "verifies WordPress files against WordPress.org's checksums," so you can confirm WordPress's own files are intact.⁸

How do you keep this from happening next time?

Measure the furniture before moving day, and you won't panic at the door.

Jeensuk's takePHP versions change every year, and every time, this move comes back. For an older site with lots of plugins, another answer is to have less to move: switch to a setup that doesn't run PHP at all.