PHP is the language most content systems are written in, and the server can run several versions side by side. Old versions stop receiving security fixes; new versions are noticeably faster. Sooner or later your host, your content system or a plugin will ask you to move up. The switch itself takes seconds. The preparation is what keeps it uneventful.
Find out what you are running
In cPanel, open MultiPHP Manager. Each domain is listed with its current version. A domain marked "inherit" uses the account's default, shown at the top. WordPress also reports the version under Tools > Site Health > Info > Server.
The PHP project publishes which versions still receive fixes on its "Supported Versions" page. If yours is past the end of security support, upgrading is not optional for long.
Before you switch
- Update everything first. Bring the content system, its theme and every plugin up to date on the current PHP version. Most breakages after a PHP change come from old plugin code, and the fix is usually an update that already exists.
- Check requirements. The content system and any paid plugins state the PHP versions they support. If something important has not been updated in years, find its replacement before the switch, not after.
- Take a backup. A PHP change does not alter files or the database, but an update made in step 1 can. The backup guide covers a quick one.
- Test on a copy if you can. A staging subdomain can be set to the new version while the live site stays on the old one. Click through it there first. The staging guide shows how to build one.
Make the change
- In MultiPHP Manager, tick the domain.
- Choose the new version from the list at the top right and press Apply.
It takes effect within moments. Subdomains with their own entry in the list are changed separately, which is exactly what makes staging possible.
Move one step at a time when you are far behind. Going from a very old version straight to the newest surfaces every problem at once; going up one or two releases, testing, and repeating keeps each round small.
What to test straight away
- The home page, a normal article and an archive or category page.
- Signing in to the admin area and saving a draft.
- Every form: contact, sign-up, search, comments.
- Anything that takes payment or sends email.
- Uploading an image.
Then open the error log. A site can look fine while a background feature fails quietly.
Reading what the log tells you
- Fatal error lines mean something is broken now. The path in the message names the plugin or theme responsible.
- Deprecated lines are warnings about the future. The site works; the code will need updating before the next PHP change. Note which plugin and move on.
- "Call to undefined function" for something that worked before usually means a PHP extension that was on in the old version is off in the new one.
Extensions and settings do not always carry over
Each PHP version has its own set of extensions and its own settings. After switching, check two places:
- MultiPHP INI Editor: upload size, memory limit and time limits for the new version. The upload limits guide explains each.
- Your host's Select PHP Version or extensions page, where it exists: confirm that the extensions your site needs, commonly ones for images, databases and zip files, are ticked for the new version.
If something breaks: roll back
Go back to MultiPHP Manager, select the previous version, and Apply. The site returns to how it was, because nothing else changed. Then use the error log to find which plugin objected, update or replace it, and try again. Rolling back is a pause, not a solution; the old version's support still ends.
Do not forget scheduled jobs
Cron jobs call PHP by a path, and that path may run a different version from the one the website uses. After the switch, run each job's command once by hand and read the output. The cron guide has the details.
Common questions
Will a newer PHP version make my site faster?
Usually, yes. Each major release has brought measurable speed gains for the same code. Caching still matters more.
My host is forcing an upgrade on a date. What if I am not ready?
Ask whether they offer extended support for the old version for a fee; some do. Use the time to replace whatever is holding you back, because the extension will end too.
Can two parts of one site use different versions?
Each domain and subdomain can have its own. Folders inside one domain normally share a version.