Different PHP Versions

[freakpants]

Hi,

We are working with concrete5 too and are moving towards developing on local docker images. Some of our sites are running on older php versions. How would we go about expanding the image to build with different versions? Would it be good practice to work with .env Variables that specificy which php version to use when building/running the image? Or should we just build a new image for every version and commit that as a tag? I'm interested in developing this as a pull request so we don't have to fork the project completely (and lose out on any future updates).