Description:
------------
When you encode a proper javascript object as json and then use the json_decode function, it fails.

The keys in Javascript objects are _not_ supposed to be quoted.  If you're going to store a json-encoded object (say in a database) and then reuse it later in javascript, quoting the keys so that php's json_decode function works means that you're counting on the browser's javascript to support something that is not supported by the javascript specification.

Reproduce code:
---------------
// In javascript, we have an object:
// var obj = { parent_id:-1,label:"label" };
//
// In javascript, the keys for objects are _not_ quoted by 
// single or double quotes.  So, if we're going to properly encode
// this to later reuse it in javascript, we get this sent to php:
$json = '[{parent_id:-1,label:"label"}]';

// Let's try to convert it:
var_dump(json_decode($json, true));

Expected result:
----------------
{ ["parent_id"]=>  int(-1) ["label"]=>  string(5) "label" }

Actual result:
--------------
NULL