usort ( array,cmp_function )

<?php
   function cmp_function(a,b) {
      if (a ==b) return 0;
      return (a>b) ? -1 : 1;
   }

   fruits = array("d"=>"lemon", "a"=>"orange", "b"=>"banana" );
   usort(fruits, "cmp_function");

   print_r($fruits);
?>

Array ( [0] => orange [1] => lemon [2] => banana )