键值对数组如何按照"键"进行排序？

$data=array(
array('id'=>8,'username'=>'eight'),
array('id'=>9,'username'=>'nine'),
array('id'=>1,'username'=>'one'),
array('id'=>5,'username'=>'five'),
);
$id_sort = array();
foreach($data as $key => $value){
$id_sort[$key] = $value['id'];
}
array_multisort($data, SORT_ASC, $id_sort);
print_r($data);
array_multisort($data, SORT_DESC, $id_sort);
print_r($data);

Array
(
[0] => Array
(
[id] => 1
[username] => one
)
[1] => Array
(
[id] => 5
[username] => five
)
[2] => Array
(
[id] => 8
[username] => eight
)
[3] => Array
(
[id] => 9
[username] => nine
)
)
Array
(
[0] => Array
(
[id] => 9
[username] => nine
)
[1] => Array
(
[id] => 8
[username] => eight
)
[2] => Array
(
[id] => 5
[username] => five
)
[3] => Array
(
[id] => 1
[username] => one
)
)