set_php_version

Change the PHP version, then confirm it by reading the version back — it never reports success on an unconfirmed write. On a CloudLinux node the change goes through the CloudLinux PHP Selector and applies to the whole hosting account (scope: account in the response); elsewhere it is per-domain. Changing PHP can break a site written for an older version, so pick a version the application supports. This does not touch php.ini (use set_php_settings) or extensions (use manage_php_extensions).