studentPointsCalculator.php

<?php

$studentFirstPoints = $_GET['a'] ?? null;
$studentSecondPoints = $_GET['b'] ?? null;


try {
    $studentPointsCalculator = new StudentPointsCalculator($studentFirstPoints, $studentSecondPoints);

    $studentPointsCalculator->studentWasApproved();

    echo 'Você foi aprovado!';

} catch (StudentCalculatorException $exception) {
    echo $exception->getMessage();
}

class StudentCalculatorException extends Exception {}

class StudentPointWasNotAvailable extends StudentCalculatorException
{
    public function __construct()
    {
        parent::__construct(StudentPointsCalculator::STUDENT_POINTS_WAS_NOT_AVALIABLE);
    }
}

class StudentWasReproved extends StudentCalculatorException
{
    public function __construct()
    {
        parent::__construct(StudentPointsCalculator::STUDENT_WAS_REPROVED);
    }
}

class StudentPointsCalculator
{
    const STUDENT_WAS_REPROVED = 'Voce foi reprovado!';
    const STUDENT_POINTS_WAS_NOT_AVALIABLE = 'Nota indisponível.';
    const MIN_FINAL_POINTS_TO_BE_APPROVED = 10;
    const MAX_FINAL_POINTS_TO_BE_APPROVED = 20;

    /**
     * @var int
     */
    private $studentFirstPoints;

    /**
     * @var int
     */
    private $studentSecondPoints;

    /**
     * @var int
     */
    private $finalPoints;

    /**
     * Student constructor.
     * @param  int|null  $studentFirstPoints
     * @param  int|null  $studentSecondPoints
     */
    function __construct(?int $studentFirstPoints, ?int $studentSecondPoints)
    {
        $this->studentFirstPoints = $studentFirstPoints;
        $this->studentSecondPoints = $studentSecondPoints;

        $this->finalPoints = ($this->studentFirstPoints + $this->studentSecondPoints);
    }

    /**
     * @return bool
     * @throws StudentPointWasNotAvailable
     */
    private function studentFinalPointsWasAvailable(): bool
    {
        if(is_null($this->studentFirstPoints) || is_null($this->studentSecondPoints)) {
            throw new StudentPointWasNotAvailable();
        }

        return true;
    }

    /**
     * @return bool
     * @throws StudentWasReproved
     * @throws StudentPointWasNotAvailable
     */
    public function studentWasApproved(): bool
    {
        $this->studentFinalPointsWasAvailable();

        if($this->finalPoints <= self::MIN_FINAL_POINTS_TO_BE_APPROVED && $this->finalPoints >= self::MAX_FINAL_POINTS_TO_BE_APPROVED) {
            throw new StudentWasReproved();
        }

        return true;
    }
}