So far, each time we have had to add a feature, we added a new PHP file with a mixture of PHP and HTML for that specific page. For chunks of code with a single purpose, and which we have to reuse, we created functions and added them to the functions file. Even for very small web applications like ours, the code starts becoming very confusing, and the ability to reuse code is not as helpful as it could be. Now imagine an application with a large number of features: that would be pretty much chaos itself.

The problems do not stop here. In our code, we have mixed HTML and PHP code in a single file. That will give us a lot of trouble when trying to change the design of the web application, or even if we want to perform a very small change across all pages, such as changing the menu or footer of the page. The more complex the application, the more problems we will encounter.

MVC came up as a pattern to help us divide the different parts of the application. These parts are known...