How to populate second dropdown based on selection of first dropdown using jQuery/AJAX and PHP/MySQL?
Solution 1:
First, your document-ready looks a bit off, it should either be $(document).ready(function(){}); or it could be just $(function(){});.
Second, you looping over the JSON result looks a bit odd as well. Try something like this instead:
$.each(data.subjects, function(i, val){
$('select#item_2').append('<option value="' + val.id + '">' + val.name + '</option>');
});