If you are running CodeIgniter 1.7.2, there is a security flaw with the file upload class. (fixed on July 12, 2010)  The easiest way to install the patch is to use the standalone patch http://codeigniter.com/download_files/CI_1.7.2_201007_sec_patch.zip and unzip the file to the Code Igniter system/libraries folder.

Here’s a quick tip to make cleaner looking URLs in CodeIgniter PHP framework. By default, if you have an application, the path of the application usually ends after index.php. Using Apache RewriteEngine, you can make cleaner looking URLs. You can have something similar to mysite.com/cigniter/MyApplication instead of mysite.com/cigniter/index.php/MyApplication