If you are using CodeIganiter 2.x, you must have encountered an issue like one given below

"Class 'MY_Controller' not found in application/controllers/welcome.php on line 3"

To resolve this issue , copy the MY_Controller.php file in application/core folder. Try again and here you go.

Ubuntu doesn't provides any package for php5 dbase support. So to install and configure php 5 dbase support you need to download the appropriate php source code from the php.net website at http://www.php.net/downloads.php for the latest one and for the old versions you can download from http://www.php.net/releases/

The procedure to configure and install php5 dbase package is mentioned here.

Ubuntu 10.10 has PHP 5.3 as default, some application are still unable to work with PHP 5.3 and require PHP 5.2. However, this script uses aptitude for re-installing the packages and since Ubuntu 10.10 aptitude isn't installed by default. I adapted the script and was able to make it work with Ubuntu 10.10.