Writing an application is easy. Writing an application that supports all characters from multiple languages? Not so easy. [...] To make your CodeIgniter application play nicely with UTF-8 you have a few things to think about.
He shows how to set the headers up correctly, change the framework's configuration to include UTF-8 as a character set and set up the database connection to use it too. If you're already using a non-UTF-8 database structure, he also includes an example of how to make the conversion.