PHP 子クラス

<?php
class Score
{
    private $subject;
    private $points;

    public function __construct($subject, $points)
    {
        $this->subject = $subject;
        $this->points = $points;
    }

    private function getResult()
    {
        return $this->points >= 80 ? "Pass" : "Fail";
    }

    public function getInfo()
    {
        return "{$this->subject}, {$this->points}, {$this->getResult()}";
    }
}

class MathScore extends Score
{
    public function __construct($points)
    {
        parent::__construct("Math", $points);
    }
}

class EnglishScore extends Score
{
    public function __construct($points)
    {
        parent::__construct("English", $points);
    }
}

class User
{
    private $name;
    private $score;

    public function __construct($name, $score)
    {
        $this->name = $name;
        $this->score = $score;
    }

    public function getInfo()
    {
        return "{$this->name}, {$this->score->getInfo()}";
    }
}

$user1 = new User("Taro", new MathScore(70));
$user2 = new User("Jiro", new EnglishScore(90));

echo $user1->getInfo() . PHP_EOL;
echo $user2->getInfo() . PHP_EOL;