What needs to be improved/learned?

Question

PHP

The prehistory is this - I got tired of Java (I have been working on it for three years), I decided to try my hand at web development (PHP). I asked a company with vacancies for juniors in this area for a test task, communication with this company did not work out, so I ask experts for feedback on the code.
The task (in my retelling because I'm not sure that I have the right to post the original): to implement a tree consisting of sections and elements using PHP and jQuery.
Link to the GitHub
project I did not use PHP frameworks in principle, because I think that you first need to figure out the basics yourself.
I understand that there is no layout.
Implemented according to the MVC scheme and added CNC (I took most of the routing ready).
I would like to know what are the mistakes and what should be learned

Answer 1

For some reason, models are stored in your controllers. That is, there is no clear separation between the model / controller - problems will arise during testing.
Have you read phptherightway.com ?
Also, as a rule, only the entry point is left in the public domain - index.php, the rest of the application code is placed one level higher. For example, in the app folder. So the structure is something like this:

app/
-controllers/
-models/
-...
public_html/
-index.php
-images/
-css
-js/
-...

nbproject in .gitignore should be thrown. And in general, the settings of any IDE should be kept locally so as not to litter in the git.