not working json with grid

http://stackoverflow.com/questions/8954253/how-to-use-json-with-extjs

by molecule

HTML

<link rel="stylesheet" href="http://dev.sencha.com/deploy/ext-4.0.7-gpl/resources/css/ext-all.css">

JavaScript

var data = {"locations":{
    "cc0001":{
        "category":[""],
        "name":"",
        "address":"",
        "lat":"",
        "long":"",
        "tel":"",
        "opening":"",
        "closing":""
    }
}
           

    var store=Ext.create('Ext.data.Store',    {
            data: data,
      autoLoad : true,
                               fields: [{ name:'id'},
                            {name: 'name'},
            {name: 'category'},
            {name: 'address'},                   
            {name: 'lat'},
            {name: 'long'},
                            {name: 'tel'},
                            {name: 'opening'},
            {name: 'closing'}],
      root: "locations",
          proxy:{
              type: 'ajax',
            url : '../descrittore/json.php?',
             method : 'GET',
                               reader: 'json'
             })
          });
store.load();


// create the grid
var grid = new Ext.grid.GridPanel({
    store: store,
    columns: [
        {header: "appeId", width: 60, dataIndex: 'id', sortable: true},
        {header: "survId", width: 60, dataIndex: 'category', sortable: true},
        {header: "location", width: 60, dataIndex: 'lat', sortable: true},
        {header: "surveyDate", width: 100, dataIndex: 'long', sortable: true},
        {header: "surveyTime", width: 100, dataIndex: 'opening', sortable: true},
    ],
    renderTo:'example-grid',
    width:540,
    height:200
});