相同的域但无法获取cookie

I am using query.cookie.js to set a cookie as in the following code:

        $.cookie('objectID', objectID);
        var theTarget = '/mvtm?page_id=4252' ;
        window.open(theTarget, "Detail").focus();

Then in the targeted page, in an iframe, I am using PHP code to access the cookie:

$variable = $_COOKIE['objectID'];

However, that index in $_COOKIE is undefined! I can see the cookie in the browser in both the page where it is set and the targeted page (using browser developer tools). These pages are all in the same domain (localhost) and the cookies are intended to be simple session cookies. Does the fact that both the set and get code above are in iframes have any bearing? I've tried this in both Safari and Firefox.

Make the cookie available across the entire domain by setting the path

$.cookie('objectID', objectID, { path: '/' });

by default it's only available on the page where it was created.