Respect\Validation - validate string if not empty, otherwise return true

Question

I'm using Respect\Validation for validate fields. Some of my fields are not mandatory, as the phone number, but if they are not empty they must be validated. Following my current code:

v::Phone()->validate($phoneNumber); // it should return true if $phoneNumber is empty

How to do it?

Answer 1

Based on the docs, it looks like it should be:

v::optional(v::Phone())->validate($phoneNumber);