如何运用PHP数组排序函数array

$arrUsers = array(
array(
'id' => 1,
'name' => '张三',
'age' => 25,
),
array(
'id' => 2,
'name' => '李四',
'age' => 23,
),
array(
'id' => 3,
'name' => '王五',
'age' => 40,
),
array(
'id' => 4,
'name' => '赵六',
'age' => 31,
),
array(
'id' => 5,
'name' => '黄七',
'age' => 20,
),
);

$sort = array(
'direction' => 'SORT_DESC', //排序顺序标志 SORT_DESC 降序；SORT_ASC 升序
'field' => 'age', //排序字段
);
$arrSort = array();
foreach($arrUsers AS $uniqid => $row){
foreach($row AS $key=>$value){
$arrSort[$key][$uniqid] = $value;
}
}
if($sort['direction']){
array_multisort($arrSort[$sort['field']], constant($sort['direction']), $arrUsers);
}
var_dump($arrUsers);