Is there any convention for naming php files?
Not talking about php class files, but files that are mostly HTML with some php inside them.
Should it be my-file-example.php
There are usually 2 conventions you need to take into consideration:
In best scenario these 2 are the same. I usually try to avoid cases when a framework tries to force some custom rules.
Either way, the MOST important is to stay consistent throughout the project. Once you pick a convention to follow, stick with it until you start working on a different project. There's nothing worse than different naming conventions in a single project, doesn't matter if we're talking about files, classes, methods or whatever. Be consistent.