CompatNav

Is my WordPress site ready for PHP 8? A safe pre-upgrade checklist

By CompatNav · Published · Last reviewed · 5 min read

Short answer

Six steps: back up your site, use a staging copy if your host offers one, find your current PHP version (Tools → Site Health → Info → Server), check your plugins and theme for the version you want, update or fix what the check finds, then switch in your hosting panel and watch the site for a week. If something breaks, switch back: your posts and pages aren’t affected.

What “ready” means

WordPress itself is ready: the WordPress core team’s compatibility page lists WordPress 7.1 as compatible with PHP 7.4 to 8.5. Your site is ready when every active plugin and your theme work on the new version too.

Each PHP version removes some old features and marks others as outdated. Code that uses a removed feature stops with a fatal error; code that uses an outdated one keeps working and only writes a deprecation notice. The steps below find both before your visitors do. If your host has already set a date, the same steps fit into a plan around that date.

1. Make a backup

Back up both parts of your site: the files and the database. Your hosting panel may have a backup tool; a backup plugin works too. Download a copy, and find out how you would restore it before you need to.

2. Use a staging copy if your host offers one

A staging copy is a private copy of your site where you can try changes first. If your hosting panel can create one, switch the staging copy to the new PHP version first and look around there. If not, the rest of the plan still works: step 6 keeps a way back open.

3. Find your current PHP version

WordPress shows it: “select Tools > Site Health from the sidebar menu, and then select the Info tab. Expand the Server section and scroll down until you see PHP version.” (wordpress.org)

WordPress admin, Tools → Site Health, Info tab, Server section open: the row “PHP version” reads 8.5.11.
Tools → Site Health → Info → Server on our test site (WordPress 7.1.2 on PHP 8.5.11). Your server details will differ.

This is the version you start from. Everything that changes between it and the version you want is what the next step has to check.

4. Check your plugins and theme for the version you want

A plugin’s page on wordpress.org shows a PHP version, but that is the minimum: WordPress’s documentation describes the “Requires PHP” header as “The required minimum version of PHP needed for use with this plugin.” (developer.wordpress.org) It doesn’t tell you whether the plugin works on the newest PHP.

So check the code itself. CompatNav, for example, reads every plugin and theme on your site and lists, for the PHP version you choose, what will break and what only shows notices. It only reads files, so it’s safe to run on the live site.

The report’s verdict: “Safe to upgrade to PHP 8.5: nothing active will break”.
The verdict when nothing active will break (fictional demo plugins).

A check that reads code can’t see problems that depend on the values a plugin works with while it runs. That’s why step 6 matters.

5. Update, then fix what’s left

  1. Update WordPress, your plugins and your theme (Dashboard → Updates), then check again: an update may already remove the problem.
  2. Still “will break” on the latest version? Contact the plugin’s developer, or replace it with a maintained alternative.
  3. Code written for your site? Send the findings to whoever maintains it.
  4. Only deprecation notices left? They don’t stop your site; they can wait for the plugin’s next update.

Not ready yet: what to do explains each option.

6. Switch, then watch for a week

  1. Switch in your hosting control panel. The setting is often called “PHP version”, “PHP Selector” or “MultiPHP Manager”; your host’s support can show you.
  2. Right away, click through your site: the home page, a post, your contact form, the checkout if you have a shop, and the admin area.
  3. For a week, look at your error log (in the hosting panel, or ask your host) for new messages.
  4. If something breaks, switch back first, then find the cause: “There has been a critical error” after a PHP update shows how.

Which version to choose, and until when each one gets security fixes, is in PHP 8.2 reaches end of life on 31 December 2026.

The checklist

PHP upgrade checklist

  • Backup made (files and database), and I know how to restore it
  • Staging copy switched to the new PHP version first (if my host offers one)
  • Current PHP version noted: ______
  • Target PHP version chosen: ______
  • Plugins and theme checked for the target version
  • WordPress, plugins and theme updated; checked again
  • Everything that “will break” fixed, replaced or taken up with its developer
  • PHP switched in the hosting panel on: ______
  • Home page, posts, forms, checkout and admin clicked through
  • Error log checked daily for a week
  • I know where to switch back

To keep it on paper, print this page: the website’s menus are left out.

Key takeaways

  • WordPress 7.1 itself works with PHP 7.4 to 8.5; your plugins and theme decide whether your site does.
  • Your current PHP version is under Tools → Site Health → Info → Server.
  • A plugin’s “Requires PHP” is its minimum version, not a promise that it works on the newest one. Check the code for the version you want.
  • You can go straight to the version you want, as long as the check covers everything that changes between your current version and that one.
  • Keep a way back: a backup, and the old PHP version still selectable in your hosting panel for a few days.

Frequently asked questions

How do I check my PHP version?

In your WordPress admin, go to Tools → Site Health, open the Info tab and then the Server section: the row PHP version shows it. Your hosting control panel shows it too.

Which version should I choose?

The newest one your host offers that your plugins and theme are ready for. WordPress recommends PHP 8.3 or greater (wordpress.org); newer versions also get security fixes for longer (php.net).

Can I go straight from PHP 7.4 to 8.5?

Yes. You don’t need to install 8.0, 8.1 and the others one after the other. What matters is that you check everything that changes between 7.4 and 8.5 before you switch, not only the changes of 8.5.

My host doesn’t offer a staging site. Now what?

Check the code on the live site (a check that only reads files is safe there), fix what it finds, make a backup, and switch at a quiet time. Know where the PHP setting is in your hosting panel, so you can switch back within a minute if something breaks.

Can I switch back?

Usually yes, in the same hosting panel setting, as long as your host still offers the old version: ask before you switch. Switching the PHP version doesn’t touch your posts, pages or settings.

Check your own site before you upgrade

CompatNav is a free WordPress plugin. It reads the code of your plugins and themes on your own server and tells you, in plain words, what will break and what will only show notices on the PHP version you choose. It never changes your code. It can’t see problems that only appear while code runs with real data, so a quick check of your site after the upgrade still matters.

Get CompatNav on wordpress.org How it works

Sources

About the code examples: each output is the real output of the code shown, run with the official PHP builds, without a php.ini, with all errors reported and displayed. Only the file path was replaced by a neutral server path.