How do I include external Libraries in CodeIgniter?

There is nothing stopping you from directly including classes and working with them however you would in a vanilla PHP setup. If it works in PHP it will work in CodeIgniter.

include(APPPATH.'libraries/Amazon/FPS/Interface.php');

Peng Kong of a3m http://code.google.com/p/a3m/ has a nice way of doing it with plugins:

Example twitter_pi.php

require_once(APPPATH.'modules/account/plugins/libraries/jmathai-twitter-async/EpiCurl.php');require_once(APPPATH.'modules/account/plugins/libraries/jmathai-twitter-async/EpiOAuth.php');require_once(APPPATH.'modules/account/plugins/libraries/jmathai-twitter-async/EpiTwitter.php');

/* End of file twitter_pi.php // Location: ./system/application/modules/account/plugins/twitter_pi.php */

In controller

$this->load->plugin('twitter');$twitterObj = new EpiTwitter($this->config->item('twitter_consumer_key'), $this->config->item('twitter_consumer_secret'));

There is one problem with this in Codeigniter 2.0 there are no plugins

Oh yes codeigniter is nice and has also support for many librarys please have a look here http://www.haughin.com/code/Include the Amazon service like this $this->load->library('s3');