Is it possible to sort the product collection based on another array that contains skus

Question

I have an array that contains some SKUs belonging to the current category.

I want to reorder the collection based on that array so that the SKUs present in my order array will come first.

For this i have been trying to edit the list.phtml file

$category = Mage::registry('current_category');
$inArray = explode(',', $category->getData('top_skus'));

usort($_productCollection, function($a, $b) use ($inArray){ 
    print_r($a);
    $aAge = $a['sku'];
    $bAge = $b['sku'];
    $aWeight = 0;
    $bWeight = 0;
    if (in_array($aAge, $inArray)) 
        $aWeight++;

    if (in_array($bAge, $inArray)) 
        $bWeight++;

    if ($aWeight != $bWeight) {
        return $aWeight > $bWeight ? -1 : 1;
    } else if ($aWeight > 0) {
        // need to sort by order which specified in array
        $aIndex = array_search($aAge, $inArray);
        $bIndex = array_search($bAge, $inArray);
        return ($aIndex == $bIndex ? 0 : ($aIndex > $bIndex ? 1 : -1));
    } else {
        // just compare age values
        return ($aAge == $bAge ? 0 : ($aAge > $bAge ? 1 : -1));
    }
});

I am getting an error like this

Warning: usort() expects parameter 1 to be array, object given  in C:\wamp\www\magento1\app\design\frontend\base\default\template\catalog\product\list.phtml on line 74

How to supply the array that contains the products to my usort? From where i will get that array?

Answer 1

I assume you are constructing the collection like this:

$_productCollection = Mage::getModel('catalog/product')->getCollection()->...;

and then calling

usort($_productCollection, ...)

it doesn't work because $_productCollection is not an array, but you figured that out from the error message (I'm just being Captain Obvious).
You can try this instead.

$productArray = (array)$_productCollection->getIterator();
usort($productArray, ...);

Answer 2

I've done this a while back for a shop that required sorting by a specific value present in the object of each item in the product collection.

For this I created a custom extension and extended the Mage_Catalog_Block_Product_List class as shown below.

class [Namespace]_[Module]_Block_Mage_Catalog_Product_List extends Mage_Catalog_Block_Product_List
{

    protected function _getProductCollection()
    {

        if( is_object(Mage::registry('current_category')) ) {
            $collection = Mage::getResourceModel('catalog/product_collection')->addCategoryFilter(Mage::registry('current_category'));
        } else {
            $collection = Mage::getResourceModel('catalog/product_collection');
        }
        Mage::getModel('catalog/layer')->prepareProductCollection($collection);

        $collection->addAttributeToSelect('category_sort_value');


        // Do some fancy sorting
        $collectionReflection = new ReflectionObject($collection);
        $itemsPropertyReflection = $collectionReflection->getProperty('_items');
        $itemsPropertyReflection->setAccessible(true); // Make it accessible

        $collectionItems = $itemsPropertyReflection->getValue($collection);

        usort($collectionItems, array("[Namespace]_[Module]_Block_Mage_Catalog_Product_List", "cmp"));

        $itemsPropertyReflection->setValue($collectionReflection, $collectionItems);

        $itemsPropertyReflection->setAccessible(false); // Return restriction back
        // End them fancyness


        $this->_productCollection = $collection;

        return $this->_productCollection;
    }


    public function cmp($a, $b) 
    {
        $a_sort = (int)$a->getData('category_sort_value');
        $b_sort = (int)$b->getData('category_sort_value');

        if ($a_sort == $b_sort) return 0;
        return ($a_sort < $b_sort) ? -1 : 1;
    }
}

This basically is a fancy version of usort for objects. Small sidenote... you need PHP 5.3 for this.