laravel_demo/app/Http/Controllers/BookController.php

<?php

// php artisan make:controller BookController
// app/Http/Controllers/BookController.php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

// Фасад DB здесь не используется; здесь используется модель
use App\Models\Book;
use App\Models\Author;

class BookController extends Controller {
	function index() {
		$books = Book::all()->load("author"); // Достать все книги

		return view("books", ["rows" => $books]);
	}

	function add() {
		return view("add_book_form", ["authors" => Author::all()]);
	}

	function view(Book $book) {
		return view("book", ["book" => $book->load(["author" => function($query) {}, "comments" => function($query) { $query->recent(); }])]);
	}

	function edit(Book $book) {
		return view("edit_book_form", ["book" => $book]);
	}

	function store(Request $request) {
		$request->validate([
			"id" => "nullable|exists:books",
			"name" => "required",
			"annotation" => "nullable",
			"pagecount" => "nullable|numeric",
			"year" => "nullable|numeric",
			"isbn" => "nullable",
			"author" => "required|exists:authors,id"
		], [
			"name" => "Книга должна иметь название.",
			"author" => "Книга должна иметь автора."
		]);

		$arr = $request;

		$book = Book::find($arr->id) ?? new Book;
		$book->name = $arr->name;
		$book->annotation = $arr->annotation;
		$book->pagecount = $arr->pagecount;
		$book->year = $arr->year;
		$book->isbn = $arr->isbn;
		$book->author_id = $arr->author;
		$book->save();

		return view("success");
	}

	function comment(Book $book, Request $request) {
		$request->validate([
			"name" => "required",
			"email" => "required|email",
			"content" => "required"
		], [
			"name" => "Укажите ваше имя.",
			"email" => "Укажите ваш email.",
			"content" => "Введите комментарий."
		]);

		$arr = $request;

		$book->comments()->create([
			"name" => $arr->name,
			"email" => $arr->email,
			"content" => $arr->content
		]);

		return view("success");
	}

	function drop(Book $book) {
		$book->comments()->delete();
		$book->delete();
		return view("success");
	}
}