1. $('#save').click(function() { 
2.   var tmp = JSON.stringify($('.dd').nestable('serialize')); 
3.   // tmp value: [{"id":21,"children":[{"id":196},{"id":195},{"id":49},{"id":194}]},{"id":29,"children":[{"id":184},{"id":152}]},...] 
4.   $.ajax({ 
5.     type: 'POST', 
6.     url: 'save_categories.php', 
7.     data: {'categories': tmp}, 
8.     success: function(msg) { 
9.       alert(msg); 
10.     } 
11.   }); 
12. });