Magento – Create Observer to Notify When Item Goes Out of Stock

Aside from the built-in RSS feed, there are two ways to actually send yourself an email - the actual answer to your actual question:

Purchase an extension:

I have no experience with this extension, but was mentioned on a StackOverflow:

http://www.magentocommerce.com/magento-connect/irzoo-lowstockreport-1278.html

Do it yourself:

Create an observer for cataloginventory/stock_item - on the save event. All models have save events provided by Mage_Core_Model_Abstract. On save, it will call your observer, you can examine the stock level at that point.

<global>
    <events>
        <cataloginventory_stock_item_save_after>
            <observers>
                <mymodule_stock_item_save>
                    <type>singleton</type>
                    <class>yourmodel/observer</class>
                    <method>lowStockReport</method>
                </mymodule_stock_item_save>
            </observers>
        </cataloginventory_stock_item_save_after>
    </events>
</global>

Observer.php:

<?php

class MyCompany_MyModule_Model_Observer
{
    public function lowStockReport($observer)
    {
        $event = $observer->getEvent();
        $stockItem = $event->getItem();

        if($stockItem->getQty() < $stockItem->getNotifyStockQty()){

            //stock is lower than the notify amount, send email

            $product = Mage::getModel('catalog/product')->load($stockItem->getProductId());

            $body = "{$product->getName()} :: {$product->getSku()} just Ran out of stock:\n\n";
            $body .= "Current Qty: {$stockItem->getQty()}\n";
            $body .= "Low Stock Date: {$stockItem->getLowStockDate()}\n";

            $mail = new Zend_Mail();
            $mail->setType(Zend_Mime::MULTIPART_RELATED);
            $mail->setBodyHtml($body);
            $mail->setFrom('lowstock@yourwebsite.com', 'Low Stock Notifier');
            $mail->addTo('youremail@gmail.com', 'Your Name Here');
            $mail->setSubject('[Notice] An Item Has Gone Out of Stock');
            $mail->send();
        }
    }
}

This sends an email every time a stock item model is saved and the quantity on-hand is lower than the notify quantity set in Admin > Catalog > Manage Products.

Hope that helps.

This is default behaviour, just tested it on a CE1.7 with sample data. I do get an error message on top of the page that says: Some of the products are currently out of stock. You could change the text to explain what the user should do (remove that item from the cart) to continue or you can set all your products invertory to allow Qty below 0 so that the item is ordered as a backorder.