I don't use codeignitor, so I can't speak with authority; however, I do know that the Zend Framework has what's called "Action Helpers" in which you extend the Zend_Controller_Action_Helper_Abstract class to put functions that would have a bunch of functions you're going to use. Then you'd call it in your main action controller (most likely somewhere in the init() or __construct() methods) with something like:
class My_Controller extends Zend_Controller_Action
{
public function init()
{
$this->_myHelper = $this->getHelper('MyHelper');
}
}
Then all of your stand-alone functions would be in the class MyHelper:
class MyHelper extends Zend_Controller_Action_Helper_Abstract
{
public function myFunction()
{
// do something...
}
}
And you'd just call it like any other OO method call....
$this->_myHelper->myFunction();
Not sure if codeignitor has that option though. If not, take a look at the Zend Framework. I've been using it for a while now, and it's pretty nice.