title: Magento filter product collection by multiple categories
body: <p>Is there an easy way to filter a product collection by multiple categories? To get all items in any of the listed categories? <code>addCategoryFilter</code> doesn't seem to allow an array.</p>
  
  <p>Is the only way to get the collections for each category of interest separately then merge them?</p>
  
  <p>I understand it used to be possible with something like</p>
  
  <pre><code>addAttributeToFilter('category_ids',array('finset'=&gt;array('1','2')))
  </code></pre>
  
  <p>or similar, but that this is no longer possible since 1.4.</p>
  
  <p>Note: I am using 1.6, and in case it's of any use, I'm using something like this:</p>
  
  <pre><code>$product = Mage::getModel('catalog/product');
  $_productCollection = $product-&gt;getCollection()
    -&gt;addAttributeToSelect('*')
    -&gt;addAttributeToFilter('status',1)
    -&gt;addStoreFilter();
  </code></pre>