title: Common functions in code igniter
body: <p>I have some common functions that I've written that I'm currently copying in to each of my controllers. An example is a method that puts together my main navigation - I'm currently copying it in to each and every one or my controllers. </p>
  
  <p>Is there any way I can put these common functions somewhere so I don't have to repeat the same code in each controller? </p>
  
  <p>I thought creating core classes in the user guide would be it but that only seems to be to extend the current core </p>