New on PHPMaster.com there's a tutorial by Rakhitha Nimesh about using the multi-language support to CodeIgniter applications. This functionality is included as a default part of the framework using internal language files.

Multi-language support, also known as internationalization, is a key feature of modern web applications. Most of the full-stack PHP frameworks come with multi-language support which enables us to dynamically present our application’s interface in different languages without duplicating the existing source code for each language. Today we’re going to discuss how we can enable multiple languages using CodeIgniter as well as a few tricks to customize the core functionality.

He shows where in the configuration to set the default language and where you'll need to put the language files so CodeIgniter can find them. Sample code shows how to load in the language files and how to pass certain values out to the view for display. He also includes an example of using CodeIgniter's own hooks system to call the language file load via a "LanguageLoader" class after the controller instance is created.