How to free database resources in symfony project?

I've found these 3 ways to do that :

Propel::close();

$databaseManager = new sfDatabaseManager();
$databaseManager->initialize();
$databaseManager->shutdown();

$connection = Propel::getConnection();
$connection->close();

Do you know some other way?

Presentation: The Beauty of Ruby

In this talk Glenn Vanderburg demonstrates some of the subtle beauty that experienced Rubyists know and love.