Geekons.com: Christian Technology Podcast

Geek-Tweak: How to write MVC PHP with CodeIgniter

• Ruby on Rails has brought the MVC code patterns into the spotlight, making several web developers very happy.
• Fortunately for us PHP developers, there are TONS of framerworks for us that use MVC in a language we already know!
• CodeIgniter is simply one of many of these frameworks. (Symfony being the most popular, CakePHP being the highest in Google searches, and at least 10 others that have been adopted by several large websites.)
• I chose CodeIgniter because of simplicity, and because I read a tutorial about it when researching the Doctrine ORM.
• So what is an MVC and ORM, and why should I care?
• ORM
  • ORM stands for Object-Relational Mapper
  • ORMs handle all of the SQL so you just handle objects
  • Easily create, modify, and maintain large databases without ever touching SQL.
  • Incredibly ideal for storing data you can think of as objects with attributes.
  • A topic for a future Geekons episode, since codeigniter doesn't even come with an ORM.
• MVC
  • MVC stands for Model, View, Controller
  • MVC is a code design pattern that can be implemented in several languages.
  • One primary goal is to separate data from display from business logic.
  • Model = Data (think database layout/schema)
  • View = Display (think actual web page that displays content)
  • Controller = Business Logic (think the script that pulls data from the Model, decides what to do with it, and then crams it into a View)
• So how do I make use of all of this?
  • Install CodeIgniter on your webserver (tutorials available on their website)
    • Extract the system folder to a local folder on the server (not accessible from the web)
    • Edit the index.php file to point to that folder
    • Edit the config.php and database.php files from the config folder with your server's settings
  • Make a database (I use MySQL managed with phpMyAdmin)
  • Make your models
    • Models are basically custom PHP classes you make that interact with your database.
    • All database activity should happen in your model.
    • You can use the Active Record instead of SQL to select, insert, and update data in your database.
    • You might have a blog model that does all your add/edit/retrieve functions, and another authentication model that handles all your users and groups
  • Make your views
    • Views are traditionally the HTML content of your site with PHP variables that have all the dynamic content (if any).
    • I love to make template views and use variables to choose what CSS files, JS files, and content files to load.
  • Make your controllers
    • Controllers are basically the brains of the operation, these are the files that actually get run when you access a URL on your website.
      • When you type in yourwebsite.com/blog/about then codeigniter loads the blog controller and executes the about function.
      • The about function might pull some data from the database by loading your blog model and executing one of those functions. Possibly: $this->blog->get_about();
      • After it grabs the data, it loads the "about_us" view and passes it the data it found in the database.
    • Controllers should handle all of the server-side logic that determines what data to retrieve or insert, and what to do with that data.
    • If you wrote a page that allowed people to post blog entries on your website, the controller would check to make sure they have permission to post, might add a few details for the database based on who is posting (such as flag the entry as a guest entry), and would then call the proper Model functions to have the data inserted.
    • Depending on whether or not an insert is successful, the controller might also display a success or error message by calling the appropriate view and sending it some details.
  • Wrap your head around how URLs get sent to controllers
    • If I had a folder inside my controller folder called "blog" and then had a file with a class in it called "entries", and that entries class had a function called "view" that accepted the argument $entry_id, then I could execute that by going to yoursite.com/blog/entries/view/1 to view the first entry.
    • Obviously you would want to consider this when creating your controllers, because you want a website that is flexible but simple.
    • You can also override how codeigniter routes things in the configroutes.php file.
  • Add some finishing touches
    • I always make my URLs look a little nicer by removing index.php from them using the rewrite script found at http://codeigniter.com/user_guide/general/urls.html
    • Make an awesome website using codeigniter and send a tweet to @geekons for me to check out and mention on a future episode!