这有点棘手,很可能下面的代码中没有涵盖一些边缘情况 - 答案也假设如下:
- 您希望减少刚刚购买的父级所有相关产品的库存水平
 
- 您只希望减少 1
 
- 没有必须满足/处理的进一步并发症或其他条件
 
代码:
所以,你显然需要先创建一个模块。config.xml 需要声明将监听的观察者checkout_type_onepage_save_order_after。(注意:您可以收听其他事件以实现您的目标)。
config.xml 将至少包含以下代码:
<?xml version="1.0"?>
<config>
    <modules>
        <YourCmpany_YourModule>
            <version>1.0.0</version>
        </YourCmpany_YourModule>
    </modules>
    <frontend>
        <events>
            <checkout_type_onepage_save_order_after>
                <observers>
                    <yourmodule_save_order_observer>
                        <class>YourCompany_YourModule_Model_Observer</class>
                        <method>checkout_type_onepage_save_order_after</method>
                    </yourmodule_save_order_observer>
                </observers>
            </checkout_type_onepage_save_order_after>
        </events>
    </frontend>
    <global>
        <models>
            <yourmodule>
                <class>YourCompany_YourModule_Model</class>
            </yourmodule>
        </models>
    </global>
</config>
然后在你的观察者中:
<?php
class YourCompany_YourModule_Model_Observer
{
    public function checkout_type_onepage_save_order_after(Varien_Event_Observer $observer)
    {
        $order = $observer->getEvent()->getOrder();
        /**
         * Grab all product ids from the order
         */
            $productIds = array();
        foreach ($order->getItemsCollection() as $item) {
            $productIds[] = $item->getProductId();
        }
        foreach ($productIds as $productId) {
            $product = Mage::getModel('catalog/product')
                ->setStoreId(Mage::app()->getStore()->getId())
                ->load($productId);
            if (! $product->isConfigurable()) {
                continue;
            }
            /**
             * Grab all of the associated simple products
             */
            $childProducts = Mage::getModel('catalog/product_type_configurable')
                        ->getUsedProducts(null, $product);
            foreach($childProducts as $childProduct) {
                /**
                 * in_array check below, makes sure to exclude the simple product actually 
                 * being sold as we dont want its stock level decreased twice :)
                 */
                if (! in_array($childProduct->getId(), $productIds)) {
                    /**
                     * Finally, load up the stock item and decrease its qty by 1
                     */
                    $stockItem = Mage::getModel('cataloginventory/stock_item')
                                    ->loadByProduct($childProduct)
                                    ->subtractQty(1)
                                    ->save()
                                ;
                }
            }
        }
    }
}