javascript - pass object via post

I have an object that looks like this

var obj = { p1 : true, p2 : true, p3 : false }

I am looking to try and pass this object as part of a post request.

however on the other end (in php) all I get is

[object Object]

How can I send an object via post?

basically what I am trying to do is

I have an input that is hidden and is created like so

<input id="obj" type="hidden" name="obj[]">

which is part of a hidden form.

when a button is pressed I have

$(#obj).val(obj);
$('form').submit();