cart.php

public function deleteProduct($id_product, $id_product_attribute = null, $id_customization = null, $id_address_delivery = 0)
    {
        if (isset(self::$_nbProducts[$this->id])) {
            unset(self::$_nbProducts[$this->id]);
        }

        if (isset(self::$_totalWeight[$this->id])) {
            unset(self::$_totalWeight[$this->id]);
        }

        if ((int)$id_customization) {
            $product_total_quantity = (int)Db::getInstance()->getValue(
                'SELECT `quantity`
                FROM `'._DB_PREFIX_.'cart_product`
                WHERE `id_product` = '.(int)$id_product.'
                AND `id_customization` = '.(int)$id_customization.'
                AND `id_cart` = '.(int)$this->id.'
                AND `id_product_attribute` = '.(int)$id_product_attribute
            );

            $customization_quantity = (int)Db::getInstance()->getValue('
            SELECT `quantity`
            FROM `'._DB_PREFIX_.'customization`
            WHERE `id_cart` = '.(int)$this->id.'
            AND `id_product` = '.(int)$id_product.'
            AND `id_customization` = '.(int)$id_customization.'
            AND `id_product_attribute` = '.(int)$id_product_attribute.'
            '.((int)$id_address_delivery ? 'AND `id_address_delivery` = '.(int)$id_address_delivery : ''));

            if (!$this->_deleteCustomization((int)$id_customization, (int)$id_product, (int)$id_product_attribute, (int)$id_address_delivery)) {
                return false;
            }

            // refresh cache of self::_products
            //$this->_products = $this->getProducts(true);
            //return ($customization_quantity == $product_total_quantity && $this->deleteProduct((int)$id_product, (int)$id_product_attribute, null, (int)$id_address_delivery));
        }

        /* Get customization quantity */
        $result = Db::getInstance()->getRow('
            SELECT SUM(`quantity`) AS \'quantity\'
            FROM `'._DB_PREFIX_.'customization`
            WHERE `id_cart` = '.(int)$this->id.'
            AND `id_product` = '.(int)$id_product.'
            AND `id_customization` = '.(int)$id_customization.'
            AND `id_product_attribute` = '.(int)$id_product_attribute);

        if ($result === false) {
            return false;
        }

        /* If the product still possesses customization it does not have to be deleted */
        if (Db::getInstance()->NumRows() && (int)$result['quantity']) {
            return Db::getInstance()->execute(
                'UPDATE `'._DB_PREFIX_.'cart_product`
                SET `quantity` = '.(int)$result['quantity'].'
                WHERE `id_cart` = '.(int)$this->id.'
                AND `id_product` = '.(int)$id_product.'
                AND `id_customization` = '.(int)$id_customization.
                ($id_product_attribute != null ? ' AND `id_product_attribute` = '.(int)$id_product_attribute : '')
            );
        }

        /* Product deletion */
        $result = Db::getInstance()->execute('
        DELETE FROM `'._DB_PREFIX_.'cart_product`
        WHERE `id_product` = '.(int)$id_product.'
        AND `id_customization` = '.(int)$id_customization.
        (!is_null($id_product_attribute) ? ' AND `id_product_attribute` = '.(int)$id_product_attribute : '').'
        AND `id_cart` = '.(int)$this->id.'
        '.((int)$id_address_delivery ? 'AND `id_address_delivery` = '.(int)$id_address_delivery : ''));

        if ($result) {
            $return = $this->update();
            // refresh cache of self::_products
            $this->_products = $this->getProducts(true);
            CartRule::autoRemoveFromCart();
            CartRule::autoAddToCart();

            return $return;
        }

        return false;
    }