> breaking the Law of Demeter

How so?

You have an instance. You're allowed to call methods or access properties of that instance. You're not supposed to call methods or access properties of properties.

So chaining is just:

    $foo.something().somethingelse().blah();

At each point you're getting a new instance and accessing that. You're never reaching inside of a property of that instance.

If GP is correct re failure propagation then this is monadic composition vs. OOP object chaining.