The tutorial (Using Zend Framework components in Code Igniter) will introduce you to an easy way to integrate the Zend Framework libraries (a lot!) into Code Igniter PHP Framework.
In particular we will build an example in which we use the Zend_Service_Flickr to retrieve images based on a specific tag ('climbing' in this tutorial).
The tutorial steps you through a quick installation of the Zend Framework, but assumes that you already have CodeIgniter installed. Then it's a simple matter of combining the two, extending the Zend Flickr service client and grabbing photos related to "climbing".