Can't initialise with User ENV Variable

[jt196]

Sorry, I'm new to Docker but after struggling with moving some of the core files outside of the container, I'm tripping at the final hurdle experiencing some problems with file permissions.

Tried to run this as a docker user on a Synology NAS using environment variables:

PGID=xxx
PUID=xxxx

Double checked all the files for ownership/permissions, they're all working, so the podcastgen isn't able to write to these directories. I'm wondering whether Synology Docker app (the only way I could get this to work) has some special commands to initialise with a specific user - or if that's container related. Apologies, but just getting my head round the tech.

What I know is, if I change the permissions thus:

chmod 777
chmod 777 <config.php>

it works, I know it's not 755, but enough for today. Do you know how to set up a user env variable?