usort inside a class

Hi,

i'm trying to build a class that sorts a multidimensional array.
I'm using the php function "usort".

I declared the comparision function as a method of my class but i'm unable to give it as argument to the function usort.

this "usort($this->arr, $this->cmpi)" gaves the following error: usort() [function.usort]: Invalid comparison function

i tried to do "usort($this->arr, 'cmpi')" but it does not work either.

Thanks


      ____________________________________________________________________________________
Be a better friend, newshound, and 
know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ