title: update session variable in yii
body: <p>I want to know how can i update my session variable, 
  in my controller, when i am on page1, 
  in my <strong>public function actionpage1()</strong>
  i have this code </p>
  
  <pre><code>$quantity=1;
  $sessionCart[] = array('product_id' =&gt; $_POST['documents'], 'document' =&gt; $productInfo-&gt;name, quantity'=&gt; $quantity);
  </code></pre>
  
  <p>so my default quantity is 1, </p>
  
  <p>And when i go to another page page2, and click on update button,</p>
  
  <p>I want my $quantity to be equal to $_post['quantity'] my new valule, 
  (this is <code>&lt;?php echo CHtml::textField('quantity', $value['quantity']); ?&gt;</code>)</p>