How to get a list of categories by product number?

I need to sort categoies by product number that means which category has large number of products is shown at the top of category list. 开发者_运维技巧So catgories list should be descending order by product number. any help would be appreciated!

I have categories and its product as following as:

category                           no of products

cell phones                                 5
cameras                                     8
computers                                   3

I would like to sort categories cameras,cell phones,computers by product number .For this sorting result i would like to use join in collection class of category.

The following code will fetch the product per category:-

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

$productCount = $productCollection->count();

You can do in this way:-

• Get an array of all categories
• Loop through them
• Fetch product collection with product count for each category (from the above code).
• Sort categories with the product count.

Hope this helps. Thanks.

If you have a collection of categories called $collection then you can do this:

$collection->setOrder('children_count', 'desc');

Edit:
To make it the default in an overridden collection use this method:

protected function _initSelect()
{
    parent::_initSelect();
    $this->setOrder('children_count', 'desc');
    return $this;
}