title: Paging not working, Extjs grid
body: <p>I made an extjs grid with a bottom toolbar to create a paging behavior, but it's not working and I don't know where is the problem, I've already done it with local data, but when i used a database it didn't work, it shows all the data at once.
  <br />
  Here's the code :<br /></p>
  
  <pre><code>Ext.require([ 'Ext.data.*', 'Ext.grid.*' ]);
  
  Ext.onReady(function() {
  var categoriesStore = Ext.create('Ext.data.JsonStore', {
      autoLoad: true,
      pageSize : 10,      
      proxy: {
             type: 'ajax',
             url: 'GridDataBase/categories.php',
             reader: {
                 type: 'json',
                 totalProperty: 'total',
                 root: 'categories',
                 idProperty: 'name'
             }            
      },
      fields : ['id','name']
  });
  
  var panelOfData = Ext.create('Ext.grid.GridPanel',{
      store : categoriesStore,
      columns : [ {
          id : 'id',
          header : "Id",
          width : 20,
          sortable : true,
          dataIndex : 'id'
      }, {
          id : 'name',
          header : "Category Name",
          width : 75,
          sortable : true,
          dataIndex : 'name'
      } ],
      //stripeRows : true,
  
          //paging bar on the bottom
      bbar: Ext.create('Ext.PagingToolbar', {
          store: categoriesStore,
          displayInfo: true,
          displayMsg: '{0} - {1} of {2}',
          emptyMsg: "No categories to display"
      }),
      autoExpandColumn : 'name',
      height : 350,
      width : 600,
      renderTo : 'grid-ex',
      title : 'Categories'
  });
  
  categoriesStore.loadPage(1);
  console.log(categoriesStore.count()); // the log here shows 0
  });
  </code></pre>
  
  <p><br />
  Here's the PHP file : 
  <br /></p>
  
  <pre><code>function GetCategories() {
      $query = "SELECT id, name FROM categorie";  
      $categories = array("categories" =&gt; array());
      @mysql_connect("localhost","superuser","SS4") or die();
      mysql_select_db("dbz"); !mysql_error () or die();
      $result = mysql_query($query);
  
      $num = mysql_num_rows($result);
      $i = 0;
  
      while ($row = mysql_fetch_assoc($result)) {
          $categories["categories"][$i] = $row;
          $i++;
      }
  
      return json_encode($categories);
  }
  echo GetCategories();
  </code></pre>