Custom payment plugin error with the order confirmation

function onPaymentNotification(&$statuses)
	{
		$vars = array();
		$filter = JFilterInput::getInstance();
		foreach($_REQUEST as $key => $value) //Se reciben todas las variables provenientes de un HTTP POST de PayU
		{
			$key = $filter->clean($key);
			$value = JRequest::getString($key);
			$vars[$key]=$value;
		}
		$this->writeToLog(print_r($vars,true)."Array Recibido\n\n\n");

		//$order_id = (int)@$vars['reference_sale'];
		$order_id = (string)@$vars['reference_sale'];
		$this->writeToLog("\n Orden #: $order_id\n\n");
		$this->writeToLog("\n 2\n\n");
		$dbOrder = $this->getOrder($order_id);
		$this->writeToLog("\n dbOrder: $dbOrder\n\n");
		$this->writeToLog("\n 3\n\n");
		$this->loadPaymentParams($dbOrder);
		$this->writeToLog("\n 4\n\n");
		if(empty($this->payment_params))
		{
			$this->writeToLog("\n payment_params vacio\n\n");
			return false;
		}