[fw-general] is there a Validator to check if at least one of a group of fields is valid?

[Ian R]

...For example, say I wanted to get contact information: either a  
phone number, an email address, or both, but NOT neither.

I'm about to create a custom validator but I'm wondering if such a  
thing already exists.  I can't seem to find anything through my  
various searches but I'm not entirely sure what to call that.

I'm just now picking up speed with ZF, it's just starting to click.   
It's very exciting!

Ian