从Mage_Sales_Model_Order_Invoice对象获取发票ID

I'm writing an observer for the sales_order_invoice_register event, I'd like to get the invoice number that has just saved. I can't find the function for retrieving that ID, none of those commented calls works. Any idea? Here the code

public function foobar($observer){

      $order = $observer->getEvent()->getOrder();
      $id_order = $order->getRealOrderId();
      $id_invoice = $observer->getEvent()->getInvoice(); // the Mage_Sales_Model_Order_Invoice object
      //$id_invoice = $id_invoice->getId();                                                                                                         
      //$id_invoice = $id_invoice->getIncrementId();                                                                                                            
      //$id_invoice = $id_invoice->getInvoiceId();                                                                                                           
      //$id_invoice = $id_invoice->getRealIncrementId();                                                                                               
      //$id_invoice = $id_invoice->getData('invoice_id');

thanks!

I know this was a while ago, but in case someone still needs help on this, hopefully the following will be of use.

Once in your observer method, use the following code to get invoice ID.

$invoice = $observer->getEvent()->getInvoice();
$invoice_id = $invoice->getData('entity_id');  // or you could also use ->getEntityId();

You can check out the sales_flat_invoice table in the Mage db (ID is the first field with the name 'entity_id'). Once you have the $invoice object, similar to any other object that inherits from the Varien_Object class, you can use Magento's getData() method to access attribute values.

Also, need to look at a different event possibly... the sales_order_invoice_register event returns "unknown" according to Mage docs. Try the sales_order_invoice_pay event for the above code.

You should use the event "sales_order_invoice_save_after" in the config.xml and in your observer.php : $observer->getEvent()->getInvoice();