CodeIgniter is an Application Development Framework - a toolkit - for people who build web sites using PHP. Its goal is to enable you to develop projects much faster than you could if you were writing code from scratch, by providing a rich set of libraries for commonly needed tasks, as well as a simple interface and logical structure to access these libraries. CodeIgniter lets you creatively focus on your project by minimizing the amount of code needed for a given task.
PHP version 5.6 or newer is recommended.
It should work on 5.3.7 as well, but we strongly advise you NOT to run such old versions of PHP, because of potential security and performance issues, as well as missing features.
Please see the license agreement.