Get ID of the last product added to the cart in magento

I am trying to get the ID of the product that was most recently added to a user’s cart. A quick google search revealed this function

Mage::getSingleton('checkout/session')->getLastAddedProductId(true);

which is also used in Mage_Checkout_Block_Cart_Crosssell. When I try calling the function in my own controller however, it returns nothing. I have tried to instantiate a core ses开发者_如何学Pythonsion via

Mage::getSingleton('core/session', array('name'=>'frontend'))

however this approach does not seem to work. I also tried to create the Crossell block and making the protected method that wraps around getLastAddedProductId function public however that returns null just like it does when I try calling it on its own.

Is there something I have to call or instantiate in order to use this function? Here’s my source listing for reference.

class Mymodule_Addcartaftermath_ItemaddedController extends Mage_Core_Controller_Front_Action {
    public function generatemessageAction() {
        $parameters = $this->getRequest()->getParams();
        if (isset($parameters['ajax_call'])) {
            $latest_item_id = Mage::getSingleton('checkout/session')->getLastAddedProductId(true);
            $response = array('response' => $latest_item_id);
            echo json_encode($response);
        } else {
            $this->_redirect('/');
        }
    }
}

I tried poking through the source code, particularly the checkout/model/session.php file in the core and I cannot seem to find the definition of the function. I also looked at it’s parent’s class definition but could not find it there either.

If this method is not available to me is there another way of retrieving the most recent item added? I know that the items are added sequentially and I could perhaps just get the last item of the list of items from the cart however this would not work in the case where the user adds the same item to the cart essentially increasing the quantity rather than actual item itself (e.g. the user adds a laptop the cart when there already is one)

The call to

Mage::getSingleton('checkout/session')->getLastAddedProductId(true);

Is actually clearing the session variable after it is read. Magento uses magic methods extensively. In this case you are using the __call magic method which in turn uses the getData() method. In Mage_Core_Model_Session_Abstract_Varien you will see that they override the default behaviour of getData() to expect the second parameter to be a boolean (The first parameter to getData is the key name for the value you are looking for). That boolean is a flag telling the session to clear the variable after reading.

You could always listen for the checkout_cart_product_add_after event and add the item to your own variable in the session. That event is actually fired on the line before setLastAddedProductId() is called.

try to grep the variable you are looking for. As they are coming from magic methods then its hard to find the exact function you are after so it's easier to see the places where data gets set than where it is used

grep '>setLastAddedProductId' app/code -rsn

to see where the product id gets set to that session variable

app/code/core/Mage/Checkout/Model/Cart.php:255:        $this->getCheckoutSession()->setLastAddedProductId($product->getId());

and then you can ask this variable (if it is set else empty())

Mage::getSingleton('checkout/session')->getLastAddedProductId();

and you can see all the things that are in checkout/session and verify if the data is there.

var_dump(Mage::getSingleton('checkout/session'));

Haven't a clue why it works this way but it works for me in Magento 1.6...

<?php
require_once ( "app/Mage.php" );
umask(0);

Mage::app("default");

Mage::getSingleton('core/session', array('name'=>'frontend'));
$session = Mage::getSingleton('checkout/session');

$lastadded = $session->getData("last_added_product_id");

print_r($lastadded);

Apparently you have to instantiate the core/session and then the checkout/session. I've tried it every other way but this is the only way I've found it to work. Perhaps someone can explain why it works this way. Hope this helps you out!