We recently had a weird situation here at work where we needed to use the Url helper of Symfony inside the actions.class.php of a module. This helper is available in the view, but not in the actions class by default.
Of course, we can include this, and this was my first approach. Simply using:
worked fine for me. However, when my co-worker updated his code from Subversion, it went BOOM. He got a rather annoying FATAL error about not being able to redeclare a function. It's weird, because it worked in my situation.