Magento - How to set order status complete after place the order

- We can set order status as complete through script after order placed.
- We need to add following code in config.xml

<sales_order_place_after>
<observers>
 <b4u_order_observer>
<type>singleton</type>
<class>Mshop_B4u_Model_Observer</class>
<method>after_order_placed</method>
 </b4u_order_observer>
</observers>
</sales_order_place_after>

- Need to write the following code in observer( mshop -> b4u -> model -> Observer.php )

public static function after_order_placed($observer) {
$event = $observer->getEvent();
$order = $event->getOrder();
$order_no   = (string) $order->getRealOrderId();

$order->loadByIncrementId($order_no);
$order->setState(Mage_Sales_Model_Order::STATE_COMPLETE, true);
$order->save();
return true;
}

- And we can create invoice also through this script. for that we need to add extra code  and the above function should look like below,


public static function after_order_placed($observer) {
$event = $observer->getEvent();
$order = $event->getOrder();
$order_no   = (string) $order->getRealOrderId();

// **** This is for creating invoice *****
$order = Mage::getModel('sales/order')->loadByIncrementId($order_no);
try {
if(!$order->canInvoice())
{
Mage::throwException(Mage::helper('core')->__('Cannot create an invoice.'));
}
  
$invoice = Mage::getModel('sales/service_order', $order)->prepareInvoice();
  
if (!$invoice->getTotalQty()) {
Mage::throwException(Mage::helper('core')->__('Cannot create an invoice without products.'));
}
  
$invoice->setRequestedCaptureCase(Mage_Sales_Model_Order_Invoice::CAPTURE_ONLINE);
//Or you can use
//$invoice->setRequestedCaptureCase(Mage_Sales_Model_Order_Invoice::CAPTURE_OFFLINE);
$invoice->register();
$transactionSave = Mage::getModel('core/resource_transaction')
->addObject($invoice)
->addObject($invoice->getOrder());
  
$transactionSave->save();
}
catch (Mage_Core_Exception $e) {
  

}

// **** This is for set as order complete *****
$order->loadByIncrementId($order_no);
$order->setState(Mage_Sales_Model_Order::STATE_COMPLETE, true);
$order->save();
return true;
}



- After that we placed order we got error message in the popup box like " you cannot manually set the order status to complete ".

- For that we need to update code in core file. i know we should not edit that. but in this case we need to edit core file.

app/code/core/Mage/Sales/Model/Order.php:

/**
     * Whether specified state can be set from outside
     * @param $state
     * @return bool
     */
    public function isStateProtected($state)
    {
        if (empty($state)) {
            return false;
        }
        return self::STATE_COMPLETE == $state || self::STATE_CLOSED == $state;
    }

Adding to the top a false return value, like so:

public function isStateProtected($state)
    {
        return false;
        if (empty($state)) {
            return false;
        }
        return self::STATE_COMPLETE == $state || self::STATE_CLOSED == $state;
    }

Then run it again and your order should complete.