How to create a event observer which trigger after a customer placed an order

Question

Magento ver. 1.9.3.2

C:\xampp\htdocs\magento1\app\code\local\Maddy\Checkout\etc\config.xml

 <?xml version="1.0"?>
<config>
    <modules>
        <Maddy_Checkout>
            <version>0.0.1</version>
        </Maddy_Checkout>
    </modules>
    <global>
         <models>
            <maddy>
                <class>Maddy_Checkout_Model</class>                
            </maddy>
        <events>
        <sales_order_place_after>
                <observers>
                    <maddy_sendsms>
                        <class>Maddy_Checkout_Model_Observer</class>
                        <method>orderSms</method>
                        <type>singleton</type>
                    </maddy_sendsms>
                </observers>
        </sales_order_place_after>
        </events>
    </global>
</config>

C:\xampp\htdocs\magento1\app\code\local\Maddy\Checkout\Model\Observer.php

  <?php
class Maddy_Checkout_Model_Observer
{
    public function orderSms(Varien_Event_Observer $observer)
    {
        $incrementId = $observer->getEvent()->getOrder()->getIncrementId();
        $custName    = $observer->getEvent()->getOrder()->getCustomerFirstname();
        $orderPrice  = $observer->getEvent()->getOrder()->getGrandTotal();
        $orderId     = $observer->getEvent()->getOrder()->getId();
        $order       = $observer->getEvent()->getOrder()
        $mobile      = trim($order->getShippingAddress()->getData('telephone'));
        echo "I am here";
        die;
        /* I will write sms api here  */
        echo "Mobile" . $mobile;
        echo "<script>alert('Just to check')</script>";

    }
}

C:\xampp\htdocs\magento1\app\etc\modules\Maddy_Checkout.xml

 <?xml version="1.0"?>
<config>
    <modules>
        <Maddy_Checkout>
            <active>true</active>
            <codePool>local</codePool>
        </Maddy_Checkout>
    </modules>
</config>

When order is placed no alert is shown.

UPDATE:
if I use event based trigger I am not able to do add to cart. If I delete this module g then add cart is working.There is no log for this.

UPDATE:1.1

After creating some observers i am came to know that never echo any thing directly in observers , even dump in log to see the output. It will not break the functionality than.

Answer 1

Try below code

app/etc/Modules/Maddy_Checkout.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Maddy_Checkout>
            <active>true</active>
            <codePool>local</codePool>
        </Maddy_Checkout>
    </modules>
</config>

app/code/local/Maddy/Checkout/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Maddy_Checkout>
            <version>0.0.1</version>
        </Maddy_Checkout>
    </modules>
    <global>
         <models>
            <maddy>
                <class>Maddy_Checkout_Model</class>                
            </maddy>
         </models>
        <events>
        <sales_order_place_after>
                <observers>
                    <maddy_sendsms>
                        <class>Maddy_Checkout_Model_Observer</class>
                        <method>orderSms</method>
                        <type>singleton</type>
                    </maddy_sendsms>
                </observers>
        </sales_order_place_after>
        </events>
    </global>
</config>

app/code/local/Maddy/Checkout/Model/Observer.php

<?php
class Maddy_Checkout_Model_Observer
{
    public function orderSms(Varien_Event_Observer $observer)
    {

        $order = $observer->getEvent()->getOrder();
        echo $incrementId = $order->getIncrementId();
        echo $custName    = $order->getCustomerFirstname();
        echo $orderPrice  = $order->getGrandTotal();
        echo $orderId     = $order->getId();        
        echo $mobile      = trim($order->getShippingAddress()->getData('telephone'));
        echo "I am here";
        die;              

    }
}

Answer 2

just replace with .

Instead of

  <checkout_onepage_controller_success_action>

replace with

<sales_order_place_after>

and your Observer.php class name should be Maddy_Checkout_Model_Observer