Warning when applying Performance Booster on a website on a Plesk server: Custom PHP directives are specified in this domain’s PHP settings.

Symptoms

• When using Performance Booster for a website, a warning is shown when trying to apply the option "Optimize PHP settings: Enables JIT compilation and the realpath cache":

  Custom PHP directives are specified in this domain's PHP settings.

• The website at Domains > example.com > PHP > Additional configuration directives already has some custom PHP directives.

Cause

Custom PHP directives are specified in this domain's PHP settings.

Resolution

Remove the custom directives and apply the optimization again:

1. Log into Plesk dashboard.
2. Go to Domains > example.com > PHP > Additional configuration directives
3. Remove all directives (even ones added by Plesk) and click Apply.
4. Go back to Domains > example.com > Performance booster and apply the settings again (the "Optimize PHP settings" option should now be available.)
5. (Optional) If there were personal directives added to the domain, they can be re-added at Domains > example.com > PHP > Additional configuration directives.