'Not valid template file' error when printing invoice programatically

Question

I'm trying to find a way to print an order's invoice programatically. For that I tried to get the url that Magento uses in backend to print an invoice but it didn't help as it uses a key that I couldn't find a way to retrieve it. I'm now trying another solution, is to code a controller function that renders the invoice pdf :

public function printOrderAction() {

        $order_id=json_decode( $this->getRequest()->getParam('order_id'));

        $orderObject = Mage::getModel('sales/order')->load($order_id);

        $invoiceCollection = $orderObject->getInvoiceCollection();
        foreach($invoiceCollection as $inv) {
            $invoice = $inv;
        }

        $pdf = Mage::getModel('sales/order_pdf_invoice')->getPdf(array($invoice));
        $this->_prepareDownloadResponse('invoice'.Mage::getSingleton('core/date')->date('Y-m-d_H-i-s').'.pdf', $pdf->render(), 'application/pdf');
    }

This function, when triggering it, gives that error Not valid template file:frontend\base\default\template\payment/info/pdf/checkmo.phtml

Is there any solution for that error? Or perhaps that there is an other simpler way to get the order's invoice ?

Answer 1

Here are code to generate invoice from the order.

    $order = Mage::getModel("sales/order")->load($order_id);

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_OFFLINE);
    $invoice->register();
    $transactionSave = Mage::getModel('core/resource_transaction')
                     ->addObject($invoice)
                     ->addObject($invoice->getOrder());

    $transactionSave->save();
}
catch (Mage_Core_Exception $e) 
{
    // YOUR EXCEPTION HANDELING
}