Use call back function to proccess Magento large collection

$orders = Mage::getModel('sales/order')->getCollection();
Mage::getSingleton('core/resource_iterator')->walk($orders->getSelect(), array(array($this,'proccessOrder')));
public function proccessOrder($args)
	{
		$order = Mage::getModel('sales/order');
		$order->setData($args['row']);
		echo $order->getIncrementId() . '<br/>';
		echo $order->getGrandTotal()  . '<br />';
		$orderAmount = $orderAmount+$order->getGrandTotal();
		echo '----------------------<br/>';
		
	}