What should you do if a site stops working after changing the PHP version?

Return the domain to the previous PHP version through the hosting control panel. This is usually the fastest way to restore service. Clear server and browser caches, then check the site again. If the panel is unavailable or the rollback does not apply, contact the host and provide the domain, old version, new version, and time of the change.

Open the PHP error log and look for the first fatal error after the switch. The file path and function name often identify an incompatible plugin, theme, or custom snippet. Messages about undefined functions, deprecated syntax, or type errors are more useful than the generic browser message shown to visitors.

Reproduce the problem on staging before making another live attempt. Update the affected component, replace abandoned software, or ask its developer for a compatible release. If you cannot identify the source, disable plugins in a controlled sequence and test with a default theme while keeping a record of each change.

Once staging works on the target PHP release, repeat the normal site checks and schedule a new production change. Keep the rollback option until forms, transactions, scheduled tasks, and administration have run successfully. Avoid editing core files to suppress the error because those changes disappear during updates and can create new security problems.