Why isn't this function working?

Question

I have declared the beats function and am trying to use it. What is the difference between var_dump(is_a($sci, 'Scissors')) and var_dump($roc->beats($sci)) ? When I run this code the first var_dump returns true and the second false. I want both to return true.

abstract Class Option
{
    private $beats;

    public function beats($opponentsChoice)
    {
        return is_a($opponentsChoice, $this->beats);
    }

}

Class Rock extends Option
{
    private $beats = 'Scissors';
}

Class Paper extends Option
{
    private $beats = 'Rock';
}

Class Scissors extends Option
{
    private $beats = 'Paper';
}

$roc = new Rock;
$pap = new Paper;
$sci = new Scissors;

var_dump(is_a($sci, 'Scissors'));

var_dump($roc->beats($sci));

Answer 1

The problem is your private variables.

private variables are scoped only to the class they are defined in. Option::$beats is a different variable than Rock::$beats .

If you change your variables to be protected instead, that will work, since all members of a class hierarchy will share protected variables (and methods).