Getting product filter by root category

Question

I'm getting all products with this code:

$collection = Mage::getResourceModel('reports/product_collection')
->addAttributeToSelect('*')
->addAttributeToFilter('size', array('in'=>$size))
->addAttributeToFilter('room', array('in'=>$room))
->addStoreFilter()
->setOrder('created_at', 'desc')
->setPage($pageNumber, $productPerPage)
->setVisibility(Mage::getSingleton('catalog/product_visibility')->getVisibleInCatalogIds());
$collection->addAttributeToFilter('price', array('gt'=>$priceL));
$collection->addAttributeToFilter('price', array('lt'=>$priceG));

Then I added this code for filter by category:

->joinField('category_id', 'catalog/category_product', 'category_id', 'product_id=entity_id', null, 'left')
->addAttributeToFilter('category_id', array('in' => $catID))

And now, this code work for filter by subcategory but doesn't work for root category. Why? And how do I solve this problem?

EDIT: I'm trying to filter by one category, multi category and root category.

Answer 1

You can try below code to get product collection for a particular category.

$productCollection = Mage::getResourceModel('catalog/product_collection')
                           ->addCategoryFilter($category);

Answer 2

You can use this one if you want the root category of current store.

$categoryId = Mage::app()->getStore()->getRootCategoryId();
$category = Mage::getModel('catalog/category')->load($categoryId);
$products = Mage::getResourceModel('catalog/product_collection')
            ->setStoreId(Mage::app()->getStore()->getId())
             ->addCategoryFilter($category);