将缺货产品放在产品列表后边

将缺货产品放在产品列表后面
Rewrite Mage_Catalog_Model_Layer:
加入以下代码：

<?phpclass Rayfox_Catalog_Model_Layer extends Mage_Catalog_Model_Layer{     public function prepareProductCollection($collection)     {          if (Mage::helper('catalog')->isModuleEnabled('Mage_CatalogInventory')) {            Mage::getModel('cataloginventory/stock_item')->addCatalogInventoryToProductCollection($collection);        }               $collection->getSelect()->order('is_in_stock desc');               //Mage::log($collection->getSelect() . '');                 return parent::prepareProductCollection($collection);     }}；