CodeIgniter is an open source web application framework for the PHP language. CodeIgniter has many features that make it stand out from the crowd. Unlike some other PHP frameworks you may have come across, the documentation is very thorough and complete—covering every aspect of the framework. CodeIgniter will also run in shared hosting environments as it has a very low footprint, yet it still has exceptional performance.

On the programming side, CodeIgniter is both PHP4 and PHP5 compatible, so it will run on the majority of web hosts out there. It also uses the Model View Controller (MVC) design pattern, which is a way to organize your application into three different parts: models—the database abstraction layer, views—the front end template files, and controllers—the business logic of your applications. In the core, CodeIgniter also makes extensive use of the Singleton design pattern. This is a way to load classes so that if they are called multiple times, the same instance of the class will be returned. This is highly useful for database connections, as you would only want one connection each time that the class is used.

CodeIgniter also has an implementation of the Active Record pattern. This makes it easy to write complex SQL queries and makes your application more readable. Active Record also allows you to easily swap and change database drivers. This allows you to write the queries in PHP and still use a MySQL backend, and also gives you the option to switch to an Oracle database –without having to rewrite the queries in your application.

CodeIgniter also comes with a number of highly useful libraries and other sets of functions that help you to build your applications. This leaves you to focus on the small part of your application that is unique, rather than the part that is used across all projects, such as database queries and parsing data.

In this chapter, we will: