I wish they had a simple Docker image available with everything setup and configurable from a single file. The installation process is complex and under documented, IMHO. But the software is pretty nice!
Why do you need Docker for a simple PHP & MySQL script? To install it you just need to setup a MySQL database and enter the credentials in the setup script. Finally, add the tracking code to your site, but that's the same for every analytics engine.
And you also need to set up a bunch of things in your web server, add the cron jobs, run the update script and hope everything still works afterwards etc.