JSON数据的一部分被解释为对象，而类似的部分则被解释为数组:为什么

我有一个php脚本，它输出text/json，输出如下：

{"labels":{"ftemp":"Full time employment only","ptemp":"Part time employment only","study":"Further study only","workstudy":"Work and Study","noavail":"Not available for work","noemp":"Unemployed","other":"Other","refusal":"Information Refused"},"employjobs":{"Cambridge Beds Co Ltd.":"Accounts Assistant","Chinese Company":"Accountant"}}

格式更漂亮，看起来像这样：

{
    "labels":
    {
        "ftemp":"Full time employment only",
        "ptemp":"Part time employment only",
        "study":"Further study only",
        "workstudy":"Work and Study",
        "noavail":"Not available for work",
        "noemp":"Unemployed",
        "other":"Other",
        "refusal":"Information Refused"
    },
    "employjobs":
    {
        "Cambridge Beds Co Ltd.":"Accounts Assistant",
        "Chinese Company":"Accountant"
    }
}

现在，对我来说，"labels"answers"employjobs"看起来都是具有键值对的json对象。但是，当我对脚本进行JQuery getJSON调用时，在返回的数据对象中，"labels"是一个对象，但"employjobs"是空数组。

我错过了什么？json字符串的两个位的格式看起来是一样的，那么为什么一个被解释为对象，另一个被理解为空数组呢？

非常感谢收到任何帮助，提前谢谢。

更新：以下是在PHP脚本中的数据通过json_encode函数之前的print_r的输出：

Array
(
    [labels] => Array
        (
            [ftemp] => Full time employment only
            [ptemp] => Part time employment only
            [study] => Further study only
            [workstudy] => Work and Study
            [noavail] => Not available for work
            [noemp] => Unemployed
            [other] => Other
            [refusal] => Information Refused
        )
    [employjobs] => Array
        (
            [Cambridge Beds Co Ltd.] => Accounts Assistant
            [Chinese Company] => Accountant
        )
)

正如您所看到的，'labels'和'employjobs'都是键值对数组，这反映在PHP脚本输出的JSON字符串中。