When

v::when(v $if, v $then, v $else)
v::when(v $if, v $then)

A ternary validator that accepts three parameters.

When the $if validates, returns validation for $then. When the $if doesn't validate, returns validation for $else, if defined.

v::when(v::intVal(), v::positive(), v::notEmpty())->validate($input);

In the sample above, if $input is an integer, then it must be positive. If $input is not an integer, then it must not me empty. When $else is not defined use AlwaysInvalid