Wrote a course on how to write maintainable PHP code for the long-term. Take a look, it might be useful and you might learn something.
https://codyssey.dev/courses/building-maintainable-php-applications-foundations
CodysseyBuilding Maintainable PHP Applications: Foundations | CodysseyOver the years of working on startups, scale-ups and enterprise products, I've noticed that most codebases end up in the same place: hard to maintain, slow to change, painful to work with.