---
title: Critical PHP error after a plugin update
description: "Every page on your WordPress site shows a critical PHP error, and it started right after a plugin update. The update is not necessarily the cause. **Why…"
url: "https://homerunner.io/docs/a-wordpress-site-showed-a-critical-php-error-on-all-pages-right-after-a-plugin-u/"
updated: "2026-10-26"
category: Setup and plugins
---

# Critical PHP error after a plugin update

Every page on your WordPress site shows a critical PHP error, and it started right after a plugin update. The update is not necessarily the cause.

**Why this happens.** A PHP syntax error in a must-use plugin (mu-plugin) file takes down every page on the site. If that error appears around the same time as an update, it can look as though the update caused it, even when the two are unrelated. One example is a language-override mu-plugin that someone on your team is editing at the same moment. Once the edit is saved correctly, the site recovers on its own within about a minute.

**What you can do.** Before assuming the update caused the problem, check whether any other changes were made to the site at the same time, including edits to mu-plugins.

Still stuck? [Contact the HomeRunner team](https://homerunner.io/contact/) with your site address and what you tried, and we take it from there.