Add php files to docker image

I am completely new to docker and have been working with basic commands.

I am trying to get a php files from a git repository and add it to a docker image that is a web app. I am also new to web apps and php, so how would you add php web files to the docker image which is running a we app?

Thanks in advance for your help.

Look into dockerfiles, also depends on how you want to do it.
Do you want to put files in the container on build or runtime?