PHP Duck Sample - Head First - Design Patterns - Chapter One

Question

This is the first question I ask from many others to come.

Someone here might call me crazy because I\'m following the mentioned book in the question\'s Title using

Answer 1

It is because when you have the class with the same name of the method, the PHP consider it as a constructor. This is already deprecated in php 7 and it will be discontinued soon. You can see it on the online documentation: http://php.net/manual/en/migration70.deprecated.php

Answer 2

The reason you are seeing Quack!<br /> output is because of this:

class Quack implements QuackBehavior {

    public function quack() {
        echo 'Quack!<br />';
    }
}

Here's your problem: If you simply run new Quack(); the quack() method is automatically being executed by php as a constructor because it is the same name as your class. -- I see you referenced Java in your question, so this shouldn't be a foreign concept to you.

new Quack(); // => Quack!<br />

---

A potentially better way

<?php

interface CanFly {
  public function fly();
}

interface CanQuack {
  public function quack();
}

abstract class Duck implements CanFly, CanQuack {

  protected $color = "DEFAULT"

  public function fly(){
    echo "I'm flying with my {$this->color} wings\n";
  }

  public function quack(){
    echo "I'm quacking\n";
  }

  public function swim(){
    echo "I'm swimming\n";
  }
}

class Mallard extends Duck {

  public function __construct(){
    $this->color = "green";
  }

  public function quack(){
    echo "My quack sounds more like a honk\n";
  }
}

$m = new Mallard();
$m->fly();
$m->quack();
$m->swim();

?>

Output

I'm flying with my green wings
My quack sounds more like a honk
I'm swimming

Answer 3

In your situation, I would personally assume that I've overlooked something when saying that an echo is being reached in the code without a call to that method. I can't see a way that this would be possible.

Reanalyze your code and look for a sneaky way that your echo 'Quack!quack!' is being reached.

Answer 4

Comment this line:

echo 'Quack!<br />';

Do you see any more quacks? If so, then there is an echo/exit/die in your code with this string!