Jordi Boggiano researched which files are common in PHP packages.

I queried GitHub's API for the file listing (only the root directory) of all PHP packages listed on packagist.org. What this let me do is look at what files are commonly present (and not), which is quite interesting to get a picture of the whole ecosystem. In total, this includes file listings from 78'992 packages (no GitHub API was harmed in the making of this blog post though). And here are a few interesting things that surfaced:

https://seld.be/notes/common-files-in-php-packages