How to use interfaces and magic methods in PHP

Question

I want to use interfaces, but some of my implementations rely on magic methods such as __invoke and __call. I have to remove signatures of methods that may be invoked magically (in any implementation) from the interface. Which leads to the anti pattern Empty Interface (Yeah, I just made that up).

How do you combine interfaces and magic methods in PHP?

Answer 1

Have all of the interface methods in your implementations dispatch to __call(). It involves a lot of crummy cut-and-paste work, but it works.

interface Adder {
    public function add($x, $y);
}

class Calculator implements Adder {
    public function add($x, $y) {
        return $this->__call(__FUNCTION__, func_get_args());
    }

    public function __call($method, $args) {
        ...
    }
}

At least the body of each method can be identical. ;)