rather then you die you Mage::log('testing');

Follow the below code

<?php
class Npm_Commission_Model_Observer extends Varien_Event_Observer
{
    public function saveorder($observer)
    {
        Mage::log('sales_order_place_after');
        $params = Mage::app()->getFrontController()->getRequest()->getParams();
        Mage::log(print_r($params,true));
    }

Make you have enable log in Magento.

To check your data var/log.

rather then you die you Mage::log('testing');

Follow the below code

<?php
class Npm_Commission_Model_Observer extends Varien_Event_Observer
{
    public function saveorder($observer)
    {
        Mage::log('sales_order_place_after');
        $params = Mage::app()->getFrontController()->getRequest()->getParams();
        Mage::log(print_r($params,true));
    }

Make you have enable log in Magento. system >> Configuration >> Developer >> Log.

To check your data var/log.