It's built with php5, uses pretty static file structure, no namespaces but an autoloader. It has around 150 source files. I must say that it was surprisingly easy to get into the code base. The fact that there are no namespaces means class names have been picked carefully, no generic stuff like "dataholder". About half the classes are entirely static and there is still a lot of assoc arrays being passed around while in other places proper classes are used. The front end is just bootstrap with a little bit of additional js and ajax where it makes sense. Still it is really easy navigating the code base and finding the right spot to extend. I hardly ever felt constrained by the project's design, if ever rather by the inconsistencies of php(5) itself. Yes, sometimes it's annoying to implement a dynamic page update via ajax by hand without fancy abstraction, but if you're not building a modern spa it's not that bad and you actually get what's going on.
That other java code base I'm involved with is about 4 years old and really modular and fancy and maven and every time something needs to be added a discussion starts on how to do it, which parts to abstract away in which way, which library or framework might be suited best, and after five trillion years coding might actually start. I might have exaggerated a bit here but that's somehow the feeling I have more and more in modern software development.