PHP interpreter in global SDKs settings

Hello;

I noticed that we could add a global PHP interpreter for the IDE by going to project settings -> Platform settings -> SDKs, but I can not add an interpreter (although PHP is installed ).

I read that it was instead spent by the PHP configuration settings, so I wonder if the addition of an interpreter is useful? Otherwise, why leave this option?

If it is, I would like to know how to configure it (there is nothing in the doc).

Thank you in advance for your help.