ext中JsonStore的url无法取得返回json格式数据

/*
var data=[{id:1,
	name:' 小王 ',
	email:'[email protected]',
	sex:' 男 ',
	bornDate:'1991-4-4'},
	{id:1,
	name:' 小李 ',
	email:'[email protected]',
	sex:' 男 ',
	bornDate:'1992-5-6'},
	{id:1,
	name:' 小兰 ',
	email:'[email protected]',
	sex:' 女 ',
	bornDate:'1993-3-7'}];
*/
var reader =new Ext.data.JsonStore({
	id:'id',
	//data:data,这里是用来本地测试调用
	root:'results',
	mode: 'local',
	url:'http://localhost:99/ext2.0/js/txt/grid.php',//返回的json数据
    autoLoad: true, 
	fields:["id","name","sex","email",{name:"bornDate",type:"date",dateFormat:"Y-n-j"}]
});
reader.load();

//alert(reader.getCount);

var colM=new Ext.grid.ColumnModel([{
	header:" 姓名 ",
	dataIndex:"name",
	sortable:true,
	editor:new Ext.form.TextField()},
	{header:" 性别 ",
	dataIndex:"sex",
	sortable:true,
	
	editor:new Ext.form.ComboBox({//transform:'sexlist',
	displayField:'sex',
	triggerAction: 'all',
	mode: 'local',
    store:sex,//store
	editable:false,
    lazyRender:true})
},
{   header:" 出生日期 ",
	dataIndex:"bornDate",
	width:120,
	sortable:true,
	editor : new Ext.form.DateField(),
	renderer:Ext.util.Format.dateRenderer('Y 年 m 月 d 日 ')},
	{header:" 电子邮件 ",
	dataIndex:"email",
	sortable:true,
	editor:new Ext.form.TextField()}
]);

var grid = new Ext.grid.EditorGridPanel({
	renderTo:"grid",
	title:" 学生基本信息管理 ",
	cm:colM,  
	store:reader,
        autoHeight: true, 
	autoExpandColumn:3
});