Parsing a JSON string to array, not object

You're trying to treat an Object like an Array, and an Object is not an Array, it is an Object.

Any time you see {} in JSON, that means "What is contained within these hallowed brackets is a dynamic object". When you see [], that means "Behold! I am an Array" (there are notable exceptions to this one: jQuery does some special work with to make itself look like an array).

So, in order to iterate through an Object, you'll want to use for... in.

// eval BAD unless you know your input has been sanitized!.
var myObj = JSON.parse('{"notempty":true}');
// personally, I use it in for... in loops. It clarifies that this is a string
// you may want to use hasOwnProperty here as sometimes other "keys" are inserted
for( var it in myObj ) console.log( "myObj["+it+"] = " + myObj[it] );

{} is an object, which contains one attribute named notempty. If you want an array, it'd have to be

[{"notempty":true}]

which is an array with a single element at index 0, which is an object with the single attribute 'notempty';.

By default, if you use encode an assoc array in php, it will become a js object when you decode. In order to have it be an array, you need to make it an array in php:

PHP:

$arr = "['notempty','notempty2','notempty3']";

Otherwise, you should convert it to an array in JS, but that seems to me a waste since looping through the object in javascript is so much easier:

Javascript:

var arr = new Array();
for(var i in obj) arr[i] = obj[i];

You can use jQuery to parse it into an array like this:

var p = [];
$.each(jsonData, function (key, val) {
    p.push([val.propertyOne, val.propertyTwo]);
});

I am presuming of course that you want to parse JSON, not an array or any other string.