javascript为php保存多维数组

这是我在php中的数据:

$userLimit = array(
    "default" => array(
         "playlistLimit" => 1,
         "mediaLimit" => 2,
            ), 
     "editor" => array(
          "playlistLimit" => 5,
          "mediaLimit" => 20,
            ), 
     "author" => array(
           "playlistLimit" => 2,
           "mediaLimit" => 10,
            ), 
      ); 

当我在php中循环这个时,我得到:

foreach ($userLimit as $k => $v) {
        var_dump($k);
    }

string(7) "default" string(6) "editor" string(6) "author"

这是正确的,这正是我想要的。

当我用javascript编辑它(并发送到服务器端)时,我会这样做:

var userLimit  = [
{
    "default": {
        "playlistLimit": "1",
        "mediaLimit": "2"
    }
},
{
    "editor": {
        "playlistLimit": "5",
        "mediaLimit": "20"
    }
},
{
    "author": {
        "playlistLimit": "2",
        "mediaLimit": "10"
    }
}
]

那么我需要在发送服务器端时对其进行序列化:

JSON.stringify(userLimit)

问题是,当它返回并在php中再次循环时,我会得到密钥:

 foreach ($userLimit as $k => $v) {
        var_dump($k);
    }

int(0) int(1) int(2)

因为数据现在看起来是这样的:

array(3) { [0]=> array(1) { ["default"]=> array(2) { ["playlistLimit"]=> string(1) "1" ["mediaLimit"]=> string(1) "2" } } [1]=> array(1) { ["editor"]=> array(2) { ["playlistLimit"]=> string(1) "5" ["mediaLimit"]=> string(2) "20" } } [2]=> array(1) { ["author"]=> array(2) { ["playlistLimit"]=> string(1) "2" ["mediaLimit"]=> string(2) "10" } } }

如何使数据在保存后不更改格式?