Understanding MVC in PHP

Coding Standards

Before you start coding a cohesive framework, you might want to sit down with your team (or yourself) and talk about coding standards. The whole idea of MVC programming revolves around reusable and standardized code. I recommend talking about, at least:

• What are your coding standards regarding variable naming and indentation? Don't start a holy war, but hammer out the basics and stick to them, especially when it comes to your foundation classes.
• Decide on a standard prefix for your functions, classes, and global variables. Unfortunately, PHP does not support namespaces. As a result, it might be a good idea to prepend your variables to avoid name collisions and confusion. Throughout this article, I've prepended my global variables, functions and classes with FR_, so as to distinguish core foundation code from simple application code.
• I highly recommend using phpDocumentor to document your code as you actually code it. I will document all of the core foundation classes as well as my initial applications in this article. At my own place of employment, I run phpDocumentor via a cron job to compile documentation frequently from my code repository.

Coding the Foundation

With all of that theory out of the way, here are the foundation classes. Be sure to read the comments for my reasonings, ideas, and implementation details. I'm presenting a combination of things I've done in the past that work for me, and the results of a few years of trial and error. By no means is this the only way to program an MVC framework, but I think it provides a good overview of how things should work.

Filesystem Layout

The basic layout is simple and somewhat strictly defined. There is a directory for includes, which will follow a specific pattern to make it easy to use PHP's new __autoload() function. Another directory is for modules, which will have their own layout. The hierarchy looks like:

• /
  • config.php
  • index.php
  • includes/
    • Auth.php
    • Auth/
      • No.php
      • User.php
    • Module.php
    • Object.php
    • Object/
      • DB.php
    • Presenter.php
    • Presenter/
      • common.php
      • debug.php
      • smarty.php
    • Smarty/
  • modules/
    • example/
      • config.php
      • example.php
      • tpl/
        • example.tpl
  • tpl/
    • default/
    • cache/
    • config/
    • templates/
      • templates_c/

You're probably thinking that's a lot of code! It is, but you'll get through it. At the end of this article and the series, you'll see that MVC programming will make your life a lot easier and speed up development time.

In the filesystem structure, all of the foundation classes live inside of includes/. The example laid out a sample module, as well. Each module has its own configuration file, at least one module file, and one template file. All modules reside in modules/. I've become accustomed to wrapping my modules in an outer-page template, which is what the tpl/ directory is for. Each "theme" or template group has its own template directory. For now, I'm going to use default/ as my outer-page template. Later I'll show how to create a presentation layer for modules that want to render themselves.