Call it this way…

array_sort($array,'index1','index2',etc.);

You can place a ! in front of the index name (e.g., !index1) to indicate a reverse sort.

Ensure these two functions are available in the source or associated includes:

function array_sort_func($a,$b=NULL) {
   static $keys;
   if($b===NULL) return $keys=$a;
   foreach($keys as $k) {
      if(@$k[0]=='!') {
         $k=substr($k,1);
         if(@$a[$k]!==@$b[$k]) {
            return strcmp(@$b[$k],@$a[$k]);
         }
      }
      else if(@$a[$k]!==@$b[$k]) {
         return strcmp(@$a[$k],@$b[$k]);
      }
   }
   return 0;
}

function array_sort(&$array) {
   if(!$array) return $keys;
   $keys=func_get_args();
   array_shift($keys);
   array_sort_func($keys);
   usort($array,"array_sort_func");       
}