EXT.js 4 - How can I view data using json with a url to grid

[Exequiel]

I don't know how to view data came from my php file to this grid, i'm using this url to use in json or ajax.
url: '<?php echo base_url();?>in dex.php/process/saveme',
can anybody help me to view some kind of data came from my php file?

Ext.create('Ext.data.Store', {
    storeId:'listofUsers',
   fields: ['username','password'],
    data:{'items':[
     	{ 'username': 'zick',  "password":"123456"},
        { 'username': 'ikki',  "password":"654321" },
    ]},
    proxy: {
        type: 'memory',
        reader: {
            type: 'json',
            root: 'items'
        }
    }
});

Ext.create('Ext.grid.Panel', {
    title: 'List of Users',
    store: Ext.data.StoreManager.lookup('listofUsers'),
    columns: [
        { text: 'Username',  dataIndex: 'username',  flex: 1},
        { text: 'Password', dataIndex: 'password' },
    ],
    height: 200,
    width: 400,
    renderTo: Ext.getBody()
});

[gits]

the easiest way is to look in Chrome's or Firefox's developer tools an inspect the XHR-requests in the network panels.

it shows you what u posted and what the request returns.