请教数组如何多条件排序

请问数组怎么多条件排序
array(
       '000-00'=>array(
                                    'qty'=>20,
                                    'price'=>200
                                  ),
       '0001-00'=>array(
                                     'qty'=>10,
                                    'price'=>100
                                  ),
      '0002-00'=>array(
                                      'qty'=>30,
                                     'price'=>50
                                 )

 )

请问怎么样先按qty由小到大排序，然后按Price由大到小排序。


------解决思路----------------------

$a = array(
       '000-00'=>array(
                                    'qty'=>20,
                                    'price'=>200
                                  ),
       '0001-00'=>array(
                                     'qty'=>10,
                                    'price'=>100
                                  ),
      '0002-00'=>array(
                                      'qty'=>30,
                                     'price'=>50
                                 )

 );
foreach($a as $k=>$v) {
  $qty[] = $v['qty'];
  $price[] = $v['price'];
}
array_multisort($qty, $price, SORT_DESC, $a);
print_r($a);

Array
(
    [0001-00] => Array
        (
            [qty] => 10
            [price] => 100
        )

    [000-00] => Array
        (
            [qty] => 20
            [price] => 200
        )

    [0002-00] => Array
        (
            [qty] => 30
            [price] => 50
        )

)