Entity,ValueObject and Aggregate in the php(DDD)

ddd.php

<?php


class BookEntity
{
    public function __construct(private int $id, private string $title)
    {
    }

    public function getId(): int
    {
        return $this->id;
    }

    public function getTitle(): string
    {
        return $this->title;
    }
}

readonly class BookValueObject
{
    public function __construct(private string $author)
    {
    }

    public function getAuthor(): string
    {
        return $this->author;
    }
}

readonly class BookAggregator
{
    public function __construct(private BookEntity $bookEntity, private BookValueObject $bookValueObject)
    {
    }
    public function getBookDetails(): string
    {
        $bookDetails = "Book Title: {$this->bookEntity->getTitle()}";
        $bookDetails .= "\nBook Author: {$this->bookValueObject->getAuthor()}";
        return $bookDetails;
    }
}

$bookAggregator = new BookAggregator(
    new BookEntity(1, 'Domain-Driven Design'),
    new BookValueObject('Eric Evans')
);
echo $bookAggregator->getBookDetails();