<?php

interface Dynamic
{
    function __call($name, $arguments);
}

class Foo
{
    public function sing()
    {
        var_dump('Do re mi!');
    }

    public function dance()
    {
        var_dump('Cha cha cha!');
    }
}

class Bar implements Dynamic
{
    public function __call($name, $arguments)
    {
        // @todo; magic
    }
}

function gimmeFoo(Foo $foo)
{
    $foo->sing();
    $foo->dance();
}

gimmeFoo(new Bar()); // works because Dynamic dodges typechecks