After digging a bit into Magento's core code, I found that you need to use $item->getProduct()->setIsSuperMode(true)
in order to make $item->setCustomPrice()
and $item->setOriginalPrice()
work.
Here is some sample code you can use within an Observer that listens for the checkout_cart_product_add_after
or checkout_cart_update_items_after
events. The code is logically the same except checkout_cart_product_add_after
is called for only one item and checkout_cart_update_items_after
is called for all items in the cart. This code is separated/duplicated into 2 methods only as an example.
Event: checkout_cart_product_add_after
/**
* @param Varien_Event_Observer $observer
*/
public function applyDiscount(Varien_Event_Observer $observer)
{
/* @var $item Mage_Sales_Model_Quote_Item */
$item = $observer->getQuoteItem();
if ($item->getParentItem()) {
$item = $item->getParentItem();
}
// Discounted 25% off
$percentDiscount = 0.25;
// This makes sure the discount isn't applied over and over when refreshing
$specialPrice = $item->getOriginalPrice() - ($item->getOriginalPrice() * $percentDiscount);
// Make sure we don't have a negative
if ($specialPrice > 0) {
$item->setCustomPrice($specialPrice);
$item->setOriginalCustomPrice($specialPrice);
$item->getProduct()->setIsSuperMode(true);
}
}
Event: checkout_cart_update_items_after
/**
* @param Varien_Event_Observer $observer
*/
public function applyDiscounts(Varien_Event_Observer $observer)
{
foreach ($observer->getCart()->getQuote()->getAllVisibleItems() as $item /* @var $item Mage_Sales_Model_Quote_Item */) {
if ($item->getParentItem()) {
$item = $item->getParentItem();
}
// Discounted 25% off
$percentDiscount = 0.25;
// This makes sure the discount isn't applied over and over when refreshing
$specialPrice = $item->getOriginalPrice() - ($item->getOriginalPrice() * $percentDiscount);
// Make sure we don't have a negative
if ($specialPrice > 0) {
$item->setCustomPrice($specialPrice);
$item->setOriginalCustomPrice($specialPrice);
$item->getProduct()->setIsSuperMode(true);
}
}
}