title: How can I persist some data with a Magento Quote Item for reference on checkout?
body: <p>I need to persist some data associated to a product and then process it on checkout. This is internal data that isn't visible to the user, however it is calculated when a user is adding an item to the cart.</p>
  
  <p>I've tried extending the Cart Model's <code>addProduct()</code> call and using:</p>
  
  <pre><code>$product-&gt;setData('some_var', $my_data);
  </code></pre>
  
  <p>However, on the checkout, when I do:</p>
  
  <pre><code>$items = $this-&gt;getOnepage()-&gt;getQuote()-&gt;getAllItems();
  
  foreach($items as $item)
  {
     echo $item-&gt;getData('some_var');
  }
  </code></pre>
  
  <p>That item doesn't persist.</p>
  
  <p>I assume it's not actually storing the item but saving all of the product id's and regenerating the collection.</p>
  
  <p>Any advice on this would be greatly appreciated.</p>