Doctor visit scheduling system
That one time when I wrote my own PHP framework for a course project.
Even back in the day, people were not exactly happy with the state of our national e-health system, which had troubles running well. So, for the fun of it, I decided to see whether I could create a very basic MVP for our PHP course work. An interesting aspect of it all was that we weren't allowed to use already existing frameworks, so of course I decided to write my own!
What I did
It was an interesting experience: PHP has a wonderfully simple life cycle for the applications that you can write with it, so I managed to come up with all sorts of nice utilities: everything from managing sessions and user accounts, to preventing SQL injection with my own lightweight ORM and even a recursive (grouped) router implementation.
Frankly, I would call none of it exactly production ready, but it was nice to build such a vertical slice, both of my own framework, as well as a simple system, which looked reasonably nice thanks to Materialize, which this site also uses.
What I learnt
Many claim that PHP isn't exactly a great language. I am inclined to agree, at least in regards to the state that it was in back in the day. However, the productivity behind the language, or something like Ruby with Ruby on Rails is hard to argue against. Sometimes, even PHP without any framework can be sufficient, albeit it's still advisable to use what others are using, for the most part.