Sorting multidimensional arrays..

I'm struggling with array_multisort, was hoping someone could give me some help. I have a multidim array, such as: $myarray[0][FIRSTNAME] = JOE $myarray[1][FIRSTNAME] = TIM $myarray[2][FIRSTNAME] = BOB $myarray[0][LASTNAME] = SMITH $myarray[1][LASTNAME] = BROWN $myarray[2][LASTNAME] = JONES $myarray[0][EXTENSION] = 2000 $myarray[1][EXTENSION] = 4000 $myarray[2][EXTENSION] = 1000 I was trying array_multisort($myarray[EXTENSION], SORT_NUMERIC, SORT_DESC), but nothing seems to be happening to the array. If anyone has any clues or can point me in the right direction, I would appreciate it. Thanks, Chad