When you are working with sessions, you might have the problem, that your message is not shown.

First add them

We have different sessions:

  • core
  • checkout
  • sales
  • customer
  • admin
  • a lot more.

For each of these sessions, we have four methods to add a message:

Mage::getSingleton('*/session')->addSuccess('Woho! It worked!');
Mage::getSingleton('*/session')->addNotice('Task was executed.');
Mage::getSingleton('*/session')->addWarning('Something went wrong.');
Mage::getSingleton('*/session')->addError('Something went horribly wrong!');

And now get them

Getting the message is easy, get the right session and call getMessages():

public function getMessages($clear=false)

Mage::getSingleton('core/session')->getMessages(true)

The parameter decides whether the messages are deleted or not.

The problem

The message block

<block type="core/messages" name="global_messages" as="global_messages"/>
<block type="core/messages" name="messages" as="messages"/>

loads only the messages of core/session:

app/code/core/Mage/Core/Block/Messages.php:79
public function _prepareLayout()
{
    $this->addMessages(Mage::getSingleton('core/session')->getMessages(true));
    parent::_prepareLayout();
}

There are a few places, where other session are loaded, e.g. \Mage_Cms_Helper_Page::_renderPage:

foreach (array('catalog/session', 'checkout/session', 'customer/session') as $storageType) {
    $storage = Mage::getSingleton($storageType);
    if ($storage) {
        $messageBlock->addStorageType($storageType);
        $messageBlock->addMessages($storage->getMessages(true));
    }
}

But unfortunately not on the product view.

The solution

In my last project we already had an observer which makes sure, that the customer is redirected after sending a contact form, therefore we used the same method to just rewrite the message to the "correct" session.

$customerSession = Mage::getSingleton('customer/session');
$coreSession = Mage::getSingleton('core/session');
foreach ($customerSession->getMessages()->getItems() as $message) {
    $coreSession->addMessage($message);
}
$customerSession->getMessages(true);

Better(?) alternative

It is possible to just add all the messages as done in \Mage_Cms_Helper_Page::_renderPage.

Make sure this is done AFTER $action->loadLayoutUpdates() / $this->loadLayoutUpdates()