Add new total to grand total using observer in Magento?

Question

I want to add some extra amount to Grand total in Magento. So in checkout page, order review section will look like this:

This extra charges will depends on some conditions.

My question is: How can I change the grand total in checkout page? For this what I did is: I create a module. Please look my code:

app/code/local/Locwiseship/Customprice/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Locwiseship_Customprice>
            <version>1.0.10</version>
        </Locwiseship_Customprice>
    </modules>
    <global>
        <events>
            <!-- Création éventuelle du lien de parrainage lors de la commande -->
            <sales_quote_collect_totals_after>
                <observers>
                    <set_custom_price_locwiseship>
                        <type>singleton</type>
                        <class>Locwiseship_Customprice_Model_Sales_Quote_Address_Total_Mytotal</class>
                        <method>collect</method>
                        <method>fetch</method>
                    </set_custom_price_locwiseship>
                </observers>
            </sales_quote_collect_totals_after>
        </events>
    </global>
</config>

app/code/local/Locwiseship/Customprice/Model/Observer.php

<?php

/**
 * @category   Locwiseship
 * @package    Locwiseship_Customprice
 */
class Locwiseship_Customprice_Model_Sales_Quote_Address_Total_Mytotal
    extends Mage_Sales_Model_Quote_Address_Total_Abstract
{
    public function __construct()
    {
        $this->setCode('mytotal');
    }

    public function collect(Mage_Sales_Model_Quote_Address $address)
    {
        parent::collect($address);

        foreach ($this->_getAddressItems($address) as $item) {
            // These two lines represent whatever logic you're 
            // using to calculate these amounts
            $baseAmt = 10;
            $amt = 10;

            // Set the item's total
            $item->setBaseMytotalAmount($baseAmt);
            $item->setMytotalAmount($amt);

            // These methods automatically take care of summing 
            // "mytotal_amount" on the quote address
            $this->_addBaseAmount($baseAmt);
            $this->_addAmount($amt);
        }
        return $this;
    }

    public function fetch(Mage_Sales_Model_Quote_Address $address)
    {
        // Naturally, this exists on the quote address because "collect" ran already
        $amt = $address->getMytotalAmount();

        if ($amt != 0) {
            $address->addTotal(array(
                'code' => $this->getCode(),
                'title' => Mage::helper('Locwiseship_Customprice')->__('My Total'),
                'value' => $amt
            ));
        }
        return $this;
    }
}

app/etc/modules/Locwiseship_Customprice.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
        <Locwiseship_Customprice>
            <active>true</active>
            <codePool>local</codePool>
        </Locwiseship_Customprice>
    </modules>
</config>

Thais is my code. But Nothing happened..This is not working.. Is this the correct approach? How can I make this working? Please help me.. I am using Magento 1.9.0.1

Answer 1

I would not recomend doing this with an observer. You should add this new total as a new column to sales_flat_quote and sales_flat_order (you can also add this new column to invoice and creditmemo).

This is what I did when I needed to add an extra total to display customers credit. In your config.xml you need to add this:

<blocks>
    <customercredit>
        <class>Company_Customercredit_Block</class>
    </customercredit>

    <adminhtml>
        <rewrite>
            <sales_order_totals>Company_Customercredit_Block_Adminhtml_Sales_Order</sales_order_totals>
            <sales_order_invoice_totals>Company_Customercredit_Block_Adminhtml_Sales_Invoice</sales_order_invoice_totals>
            <sales_order_creditmemo_totals>Company_Customercredit_Block_Adminhtml_Sales_Creditmemo</sales_order_creditmemo_totals>
        </rewrite>
    </adminhtml>

    <sales>
        <rewrite>
            <order_totals>Company_Customercredit_Block_Sales_Order</order_totals>
            <order_invoice_totals>Company_Customercredit_Block_Sales_Invoice</order_invoice_totals>
            <order_creditmemo_totals>Company_Customercredit_Block_Sales_Creditmemo</order_creditmemo_totals>
        </rewrite>
    </sales>
</blocks>

<fieldsets>
    <sales_convert_quote_address>
        <base_customer_credit>
            <to_order>*</to_order>
        </base_customer_credit>
        <customer_credit>
            <to_order>*</to_order>
        </customer_credit>
    </sales_convert_quote_address>
</fieldsets>

<sales>
    <quote>
        <totals>
            <customer_credit>
                <class>Company_Customercredit_Model_Sales_Credit</class>
                <after>subtotal,discount,shipping,tax</after>
                <before>grand_total</before>
            </customer_credit>
        </totals>
    </quote>

    <order_invoice>
        <totals>
            <customer_credit>
                <class>Company_Customercredit_Model_Sales_Invoice</class>
                <after>subtotal</after>
            </customer_credit>
        </totals>
    </order_invoice>

    <order_creditmemo>
        <totals>
            <customer_credit>
                <class>Company_Customercredit_Model_Sales_Creditmemo</class>
                <after>subtotal</after>
            </customer_credit>
        </totals>
    </order_creditmemo>
</sales>

Then your block classes should look like this:

class Company_Customercredit_Block_Adminhtml_Sales_Order extends Mage_Sales_Block_Order_Totals
{
    protected $_code = 'credit';

    protected function _initTotals()
    {
        $helper = $this->getCreditsHelper();
        parent::_initTotals();
        $creditAmount = $this->getOrder()->getCustomerCredit();
        $baseAmount = $this->getOrder()->getBaseCustomerCredit();

        if ($creditAmount != 0)
        {
            $this->addTotal(
                new Varien_Object(
                    array(
                        'code' => $this->_code,
                        'value' => -$creditAmount,
                        'base_value' => -$baseAmount,
                        'label' => $helper->__('Company Credit'),
                    )
                ));
        }
        return $this;
    }

    /**
     * Get credits helper.
     * @return Company_Customercredits_Helper_Data
     */
    protected function getCreditsHelper()
    {
        return Mage::helper('customercredit');
    }

}

Here you have some nice links with a more detail explanaition: http://www.classyllama.com/blog/unravelling-magentos-collecttotals-example http://astrio.net/blog/magento-development-add-total-row-checkout/