PHP can be super hacky and super structured, within the same file, and it's your choice. You can have tests, static analysis, etc etc, or not. Or you can start without and then adding it as the project mature, without having to necessarily switch to another language.

I'm working on my own startup that started as a side project and it was super hacky at the beginning, but by sticking to PHP (and thanks to PHP continuous improvements) I was able to refactor little by little and make the codebase way more structured and easier to maintain.