php fpm – Change user php with docker-compose

The documentation for the PHP Docker image states: "To run the FPM variants as an arbitrary user, you must use the –user flag to run the fixed menu".

I'm using PHP in docker-compose and I want to change the user ID of my fpm user to 1000. What is the equivalent syntax in docker-compose?

I can not get it back in the docker-compose documentation. Maybe it's just late or that I'm stupid or something, but I do not understand.

All pointers would be appreciated.

Thank you