Does Zend Framework have a nl2br filter? I can't see it - am I just missing it?
I imagine I could do the same thing with PregReplace...
When we have an existing PHP function nl2br it really begs the question: "do we really need to wrap a ZF filter class around a function?"
There are a few filters that actually do that.
In terms of forms for injecting a filter (and maybe other cases) I would say yes or when we need some more flexibility with additional options; basically extending the PHP function. I don't really see a need for this particular function and you should be fine to simply use PHP out of the box.