Running one site on an older PHP than the rest

Somewhere in an estate of sites there is always one that cannot move yet. An old plugin, a theme nobody maintains, a custom script written against a version that has since dropped a function. The rest of the network wants the current PHP for speed and security; that one site wants to be left alone.

PHP version is set per account, so you can have both.

Change it for one account

1. Open the account's PHP Version panel.
2. Pick the version from the list.
3. Save. The change applies to that account only.

Nothing else on the server moves. The account next to it keeps whatever it was on.

Test before you assume it is fine

A version change takes effect immediately, and a site that fails will fail on the next request rather than at a convenient moment. After changing:

• Load the home page and one dynamic page, not just the front page.
• Submit something: a contact form, a login, a search.
• Read the error log rather than trusting the visual check. Deprecation notices appear there before they become fatal errors in the next version.

If it breaks, switch back. The rollback is the same three steps and takes effect just as quickly.

Extensions travel with the version

Each version has its own set of enabled extensions. Moving an account from one version to another can leave it without something it depended on, and the symptom is usually a blank page rather than a clear message. If a site fails after a version change and the error log mentions an undefined function, an extension is the first thing to check.

Treat old versions as a countdown, not a setting

Leaving one account on an old version is a reasonable decision. Forgetting that you did is not. Unsupported PHP stops receiving security fixes, and an unpatched interpreter under a public site is a standing risk that grows quietly.

Write down which account is behind and why, with a date to revisit. On a network the failure mode is not one site staying old; it is nobody remembering which ones did, until an audit or an incident finds them.

Moving the whole estate

When you do upgrade broadly, do it in waves rather than at once: a low traffic site first, then a representative one, then the rest. If something is going to break on a shared theme or plugin, the first wave finds it while the damage is small.

The PHP supported versions page lists which releases still receive security support, which is the only date that really decides how long you can wait.