your object has keys, not indices:
var task = data.task;
var id = data.id;
and you need to use $_POST ($_FORM?) not $_GET in php...
if you like GET, just build the url by hand instead of using jQuery's data tool...
BROWSER STATS [% share]
(2013/10/31) IE7:0.5, IE8:8.6, IE9:5.3, IE10:12.3, FF:17.7, CH:41.8, SF:8.1, MOBILE:20.4