On the Laravel News site there's a new post sharing some improvements with "unique" and "exists" validation that will be a part of the framework starting in version 5.3.18.
Validating requests in Laravel is simple with its ValidatesRequests trait that is automatically included through the BaseController.
It’s powerful and provides a lot of useful rules for common use cases. Two rules, exists() and unique(), are used to validate against data stored in your database. [...] The style of this is not the easiest to remember and it’s something you almost always have to consult the docs on.
Starting with Laravel v5.3.18 both of these rules have been simplified with an introduction of a new Rule class.
They include some code examples of using this new
Rule class and how to use it right along side the current validation rule format for more complex validation needs. There's also a mention of an extra "bonus" that comes with the functionality: a conversion method for translating new rules back into strings.