In this post to his site Phillip Shipley talks about Docker and how using it for your PHP deployments can make it much easier to upgrade to PHP 7.
Last year at php[tek] 2015 during the hack time I messed around and created a Docker image to run and test PHP7. It was surprisingly easy and I quickly learned that the app I was working on at the time ran fine in PHP7, good deal. So since then I’ve been awaiting the general availability release of PHP7 to move forward with upgrading my apps.
The main thing holding me back was I just didn’t want to maintain an image based on compiling from source. Not that it’s a problem, it just didn’t feel as clean and simple as using supported packages.
He points out that Ubuntu 16.04 was released and that does now have PHP 7 as a standard package so he's happily upgrading. He gets into a bit of detail about how upgrade process and some of the smaller issue he faced along the way. He also includes the update to his Dockerfile he made to change to PHP 7 (only a few characters) to rebuild with PHP 7.0.4.