CI Memory Usage

[eluser]sleddog[/eluser]
Update from thread: http://ellislab.com/forums/viewthread/75649/

use $CI =& get_instance(); as opposed to global $CI;

Still have an open question about the 2 points tonanbarbarian made:

1. Do not put the CI instance into a static variable as it will use extra memory
2. Do not add the CI instance as a property of an object as it will use extra memory