- Plesk 12.5 for Linux
Note: This article has the reference to the issue with the fix available:
PHP version is automatically switching on a subdomain without any intervention.
PHP handler or settings on primary domain were updated and propagated to the subdomain.This is Plesk internal issue with ID #PPPM-4617 , which is considered to be fixed in future Plesk updates.
Set handler of the proper PHP version manually via Plesk user interface: Subscriptions > subscription_name > Websites & Domains > Hosting Settings .