PHP中的usort() 函数是非稳定排序怎么办？

项目有个需求
一组数据，先按参数1进行排序，参数1相同的，再按参数2进行排序。
如果usort是稳定排序的话，直接用usort把数组按参数2进行排序，再把排序后的数组按参数1进行排序。
但是经过试验，usort竟然是不稳定排序，怎么办？
代码如下：

<?php$a1 = array('key1'=>1,'key2'=>1);$a2 = array('key1'=>2,'key2'=>2);$a3 = array('key1'=>2,'key2'=>3);$a = array($a3,$a2,$a1);usort($a,"my_sort2");print_r($a);usort($a,"my_sort1");print_r($a);function my_sort1($a,$b){if ($a['key1']==$b['key1']) return 0;return ($a['key1']<$b['key1'])?-1:1;}function my_sort2($a,$b){if ($a['key2']==$b['key2']) return 0;return ($a['key2']<$b['key2'])?-1:1;}?>

输出如下：

Array(    [0] => Array        (            [key1] => 1            [key2] => 1        )    [1] => Array        (            [key1] => 2            [key2] => 2        )    [2] => Array        (            [key1] => 2            [key2] => 3        ))Array(    [0] => Array        (            [key1] => 1            [key2] => 1        )    [1] => Array        (            [key1] => 2            [key2] => 3        )    [2] => Array        (            [key1] => 2            [key2] => 2        ))

这种情况下，只能自己写个插入排序之类的稳定排序算法了吗？

回复讨论(解决方案)

$a1 = array('key1'=>1,'key2'=>1);$a2 = array('key1'=>2,'key2'=>2);$a3 = array('key1'=>2,'key2'=>3);$a = array($a3,$a2,$a1);foreach($a as $v) {  $r2[] = $v['key2'];  $r1[] = $v['key1'];}array_multisort($r1,$r1, $a);print_r($a);

Array(    [0] => Array        (            [key1] => 1            [key2] => 1        )    [1] => Array        (            [key1] => 2            [key2] => 2        )    [2] => Array        (            [key1] => 2            [key2] => 3        ))

多维数组排序用这个array_multisort
http://php.net/manual/zh/function.array-multisort.php

<?php$a1 = array('key1'=>1,'key2'=>1);$a2 = array('key1'=>2,'key2'=>2);$a3 = array('key1'=>2,'key2'=>3);$a = array($a3,$a2,$a1);foreach($a as $v){     $ar1[] = $v['key1'];     $ar2[] = $v['key2'];}array_multisort($ar1,SORT_ASC,$ar2,SORT_ASC, $a);print_r($a);?>

Array
(
    [0] => Array
        (
            [key1] => 1
            [key2] => 1
        )

    [1] => Array
        (
            [key1] => 2
            [key2] => 2
        )

    [2] => Array
        (
            [key1] => 2
            [key2] => 3
        )

)

多谢两位指点 @xuzuning @傲雪星枫