通过产品ID得到collection！！！

$products->addAttributeToFilter('entity_id', array('in'=>array(10,12)));

当然这种方式的上面，必须用  ->addAttributeToSelect();

下面这种方式比较实用的，如果想按照名字排序，那么使用方法：setOrder("name","asc");如果想按照ids中的排列的顺序，那么实用
   $collection->getSelect()->order("find_in_set(e.entity_id,'".implode(',',$ids)."')");
  此为zf框架！

$idss = Mage::registry("idss");
$ids =  explode(",",$idss);

 //= array(3552,3553,3554,3555);
        $collection = Mage::getModel('catalog/product')->getCollection()
        ->addAttributeToSelect('*')
        ->addAttributeToFilter('entity_id',$ids);
    //    ->setOrder("name", "asc");

        $collection->getSelect()->order("find_in_set(e.entity_id,'".implode(',',$ids)."')");
       
        $this->setCollection($collection);