How to server static files from an php-fpm image over an nginx image

I have a web app based on the Symfony framework.

I have an php-fpm image with all the php and asset files.

Now I want to serve the files over a nginx container. The php part is easy. But how can I serve the static files included in the php-fpm image?

I tried to create a volume that is mounted by both containers. But after docker copied the files from the image into the volume after the first start the files are not updated any more after I update the image.

I could copy the files after any start of the container from a second dir into the volume to solve this problem but I dont want this overhead.

Does any one has a good idea who I can share the static files so that they can be served directly by the nginx container?

Source: StackOverflow