Interface with no parameters

Question

I have a question about interfaces. Can I have an interface specify a method with no parameters, but still have parameters in the class?

interface FooInterface {
    public function bar();
}

class Foo implements FooInterface {
    public function bar($parameters = array())
    {
        return 'bar';
    }
}

I don't get an error doing this locally in PHP 5.5.10, but do in PHP 5.4.0.

Answer 1

The problem is that the declaration of the bar method in the Foo class is actually not compatible with the declaration in FooInterface.

FooInterface::bar is a method with no parameters, Foo::bar has one parameter (though an optional one). This throws an exception in earlier PHP 5.4.x versions.

Apparently, in later versions the PHP devs have decided that it's ok to declare a method with more parameters than the interface or parent class, as long as the parameters are optional.

EDIT:

The PHP documentation states:

Furthermore the signatures of the methods must match, i.e. the type hints and the number of required arguments must be the same. For example, if the child class defines an optional argument, where the abstract method's signature does not, there is no conflict in the signature.

So the behaviour you're experiencing appears to be a bug in earlier versions of PHP. Unfortunately, I was not able to find a bug report or release note which would indicate when, and for which PHP versions, the bug was fixed.

The lowest version I could test on right now was PHP 5.4.9, and the bug appears to be fixed there, as I could run the code without errors.