php - sort Magento collection AFTER load

Question

The Magento collection sorting functions (e.g. Mage_Eav_Model_Entity_Collection_Abstract::addAttributeToSort) work by adding an ORDER BY clause to the SQL select statement. However, there are times when a collection has already been loaded and it is necessary to sort the collection.

It is certainly possible to use the toArray($fields) function and then PHP array sorting functions (either native or user-defined), however this is a little clumsy. It also means that the objects in the collection are converted to "dumb" rows of values without magic getters/setters which can/are be implemented with algorithms, etc.

I'm wondering if there are more elegant/Magento-esque methods of sorting the collection.

Thanks,
Jonathan

Answer 1

There is no proper way of doing it. But I think it is possible with using of Reflection. You can retrieve $_items property of collection object, sort them and set it back to the collection.

function sortCollection(Varien_Data_Collection $collection, callable $sorter) {
    $collectionReflection = new ReflectionObject($collection);
    $itemsPropertyReflection = $collectionReflection->getProperty('_items');
    $itemsPropertyReflection->setAccessible(true); // Make it accessible

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

    usort($collectionItems, $sorter);

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

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

    return $collection;
}