php 二维数组排序

<?php
$users = array(
            array(
                'name' => 'tom',
                'age' => 20
            ),
            array(
                'name' => 'anny',
                'age' => 18
            ),
            array(
                'name' => 'jack',
                'age' => 22
            )
);
$ages = array();
foreach ($users as $user) {
    $ages[] = $user['age'];
}
array_multisort($ages, SORT_DESC, $users); //SORT_DESC:降序---SORT_ASC:升序
print_r($users);