在magento中添加新产品时从购物车中删除商品

I want to delete items from cart while adding new products. I am observing : checkout_cart_add_product_complete event for this. My code is following:

<checkout_cart_add_product_complete>
    <observers>
        <secodaryproduct>
            <type>singleton</type>
            <class>secodaryproduct/observer</class>
            <method>checkoutCartAddProductAddComplete</method>
        </secodaryproduct>
    </observers>
</checkout_cart_add_product_complete>

And for deleting products:

 $quote = Mage::getSingleton('checkout/cart'); 
 $quote->removeItem($product['item_id']);
 $quote->save();

When i call this code without observer then this works fine and delete required items. But if i use this using observer then items not deleting from cart. I have also put the output in log file and item ids are printing correctly but my items are not deleting from cart. Please help.

When Mage::dispatchEvent('checkout_cart_add_product_complete', ...) gets invoked in /checkout/cart/add, the relevant Mage_Catalog_Model_Product instance gets passed to the event observers. So you should be able to do something like this, which will remove all cart items matching that product ID:

public function checkoutCartAddProductAddComplete(Varien_Event_Observer $observer)
{
    /* @var Mage_Catalog_Model_Product $product */
    $product = $observer->getProduct();
    /* @var Mage_Checkout_Model_Cart $cart */
    $cart = Mage::getSingleton('checkout/cart');
    $cartItems = $cart->getItems();
    /* @var Mage_Sales_Model_Quote_Item $item */
    foreach ($cartItems as $item) {
        if ($item->getProductId() == $product->getId()) {
            $cart->removeItem($item->getId());
        }
    }
    $cart->save();
}