Library.php

<?php

require_once "AbstractLibrary.php";
require_once "Author.php";

class Library extends AbstractLibrary {

    public function addAuthor(string $authorName): Author
    {
        $author = new Author($authorName);
        $this->authors[] = $author;
        return $author;
    }

    public function addBooksForAuthor(string $authorName, Book $book)
    {
        $author = $this->findAuthor($authorName);
        if ($author) {
            $author->addBook($book->getTitle(), $book->getPrice());
        }
    }
    /**
     * @param string $bookName
     */
    public function search($bookName): ?Book
    {
        foreach ($this->getAuthors() as $author){
            foreach ($author->getBooks() as $book){
                if( $book->getTitle() === $bookName){
                    return $book;
                }
            }
        }
        return null;
    }

    public function print(){

        foreach ($this->getAuthors() as $author){
            echo $author->getName().PHP_EOL;
            echo "_____________________".PHP_EOL;
            foreach($author->getBooks() as $book){
                echo $book->getTitle(). " ---". $book->getPrice().PHP_EOL;
            }
        }
    }
}