Magento filter product collection by multiple categories

Question

Is there an easy way to filter a product collection by multiple categories? To get all items in any of the listed categories? addCategoryFilter doesn\'t seem to

Answer 1

Here's a method that doesn't require modifications to core. It's taken from this post with the addition of the 'group' clause to handle duplicate product records.

$categories = array(7,45,233);

        $collection = Mage::getModel('catalog/product')->getCollection()
            ->addAttributeToSelect('*')
            ->joinField('category_id',
                'catalog/category_product',
                'category_id',
                'product_id=entity_id',
                null,
                'left')
            ->addAttributeToFilter('category_id', array('in' => $categories));
        $collection->getSelect()->group('e.entity_id');