Additional PHP directives for a domain disappeared or got changed when the Subscription of the domain was synchronized with its Service Plan
The Subscription tied to this domain is not in a Locked state and is therefore able to be synchronized with the Service Plan
It is expected behavior for a domain under a Subscription to get overwritten Additional PHP directives if they are changed for the Service Plan and the Service Plan is later synchronized with the Subscriptions that are using it.
Note: Additional PHP directives will be propagated to all Subscriptions linked with the Service Plan that are not in a Locked state.
Additional PHP directives settings set for a Service Plan will become the default ones for objects on lower levels, such as Subscriptions and Domains that are using this Service Plan.
Settings configured on the Service Plan level will become the default for all Subscriptions that are not in a Locked state and are using that Service Plan, while settings configured on the Subscription level will become the default for all Domains using that Subscription.
A Subscription reaches a Locked state automatically, only if there were some customization changes in it that are clearly forbidden for a customer according to the Service Plan permission settings.
Since a Service Plan cannot provide permissions for customers to modify additional PHP directives, any changes in Additional PHP directives settings will not lock the Subscription automatically, however that can still be done manually.
As a workaround, you can apply either one of the following (based on your specific situation):
Find which Subscription your domain is using and change the status of the Subscription to Locked manually by following these steps:
1. Go to Plesk > Domains > press on Customize in the right sidebar
2. Do not make any changes to settings on this page
3. Scroll down to the bottom and press Apply & Lock
Note: This will put the Subscription in a Locked status and will thus not allow it to get synchronized with any changes that are made on the Service Plan level. Any changes to Additional PHP directives settings for domains using this Subscription will not be overwritten via the Service Plan update process
Create a separate Service Plan Addon that would contains the PHP directives in Plesk by doing the following:
1. Go to Plesk > Service Plans > Hosting (Reseller) Plans > Add an Add-on
2. Configure the Addon by specifying required PHP directives in PHP Settings tab > Additional configuration directives
3. Add this newly created addon to the necessary Subscription in Plesk > Subscriptions > example.com > Change plan/add-ons (right sidebar) > New Service Plan Addon
Note: This change will need to be made for every Subscription separately