PHP Interface vs. Ruby Duck Typing

duck_typing.rb

class Cambio
  def aumentaMarcha
    @marcha += 1
  end
  
  def diminiuMarcha
    @marcha -= 1
  end
end

class Carro
  def initialize(cambio)
    raise Exception("Esse cambio nao funcio") unless cambio.respond_to(:aumentaMarcha)
  end
end

interface.php

<?php

interface Cambio {
  private $marcha
  public function aumentaMarcha();
  public function diminuiMarcha();
  public function podeAumentar();
  public function podeDiminuir();
}

class Carro {
  public function __construc(Cambio $cambio) {
    $this->cambio = $cambio;
  }
  
  public function acelera() {
    $this->cambio->aumentaMarcha();
  }
}