Question

I’m trying to find products that are in two categories.
I’ve found an example to get products that are in category1 OR category2.
http://www.alphadigital.cl/blog/lang/en-us/magento-filter-by-multiple-categories.html
I need products that are in category1 AND category2.

The example in the blog is:

class ModuleName_Catalog_Model_Resource_Eav_Mysql4_Product_Collection
  extends Mage_Catalog_Model_Resource_Eav_Mysql4_Product_Collection{

  public function addCategoriesFilter($categories){

  $alias = 'cat_index';
  $categoryCondition = $this->getConnection()->quoteInto(
    $alias.'.product_id=e.entity_id AND '.$alias.'.store_id=? AND ',
    $this->getStoreId()
  );

  $categoryCondition.= $alias.'.category_id IN ('.$categories.')';

  $this->getSelect()->joinInner(
    array($alias => $this->getTable('catalog/category_product_index')),
    $categoryCondition,
    array('position'=>'position')
  );

  $this->_categoryIndexJoined = true;
  $this->_joinFields['position'] = array('table'=>$alias, 'field'=>'position' );

  return $this;

  }
}

When I’m using this filter alone it perform OR query on several categories.
When I combine this filter with prepareProductCollection of Mage_Catalog_Model_Layer
it somehow remove the filter effect.

How can I change the filter to AND and combine it with prepareProductCollection?

Thanks

Thanks

Answer 1

This code will allow you to filter by multiple categories but avoid completely killing performance if you had to perform multiple collection loads:

$iNumberFeaturedItems = 4;
$oCurrentCategory = Mage::registry('current_category');
$oFeaturedCategory = Mage::getModel('catalog/category')->getCollection()
        ->addAttributeToFilter('name','Featured')
        ->getFirstItem();
$aFeaturedCollection = Mage::getResourceModel('catalog/product_collection')
        ->addAttributeToSelect(array('name', 'price', 'small_image', 'url_key'), 'inner')
        ->addStoreFilter()
        ->addCategoryFilter($oFeaturedCategory)
        ->addCategoryIds();

The first step is to get a collection of products for one category (in this case, a Featured category). Next step is to get the IDs of the products, notice that this does NOT perform a load (ref Mage_Core_Model_Mysql4_Collection_Abstract::getAllIds())

    $aFeaturedProdIds = $aFeaturedCollection->getAllIds();
    shuffle($aFeaturedProdIds);  //randomize the order of the featured products

Then get the IDs for a second category:

    $aCurrentCatProdIds = $oCurrentCategory->getProductCollection()->getAllIds();

And intersect the arrays to find product IDs that exist in both categories:

    $aMergedProdIds = array_intersect($aFeaturedProdIds,$aCurrentCatProdIds);

For this particular use case, we loop until we have sufficient intersecting products, traversing up the category tree until we find a large enough match (but stopping at root category!):

    while(count($aMergedProdIds) < $iNumberFeaturedItems && $oCurrentCategory->getId() != Mage::app()->getStore()->getRootCategoryId()): 
        $oCurrentCategory = $oCurrentCategory->getParentCategory();
        $aParentCatProdIds = $oCurrentCategory->getProductCollection()->getAllIds();
        $aMergedProdIds = array_intersect($aFeaturedProdIds,$aParentCatProdIds);
    endwhile;

Finally, filter our initial collection by the IDs of the intersecting products, and return.

    $aFeaturedItems = $aFeaturedCollection->addIdFilter(array_slice($aMergedProdIds,0,$iNumberFeaturedItems))->getItems();
    return $aFeaturedItems;