<s>[INST] This is a follow up to the previous post on the MyBook project. In this post, I'll cover the implementation of a simple CRUD (Create, Read, Update, Delete) application with Backbone.js and a simple RESTful API using PHP.

I'm just going to show a few key parts of the code. Let's start with the models.
```javascript
// models/Book.js
var Book = Backbone.Model.extend({
  defaults: {
    title: '',
    author: '',
    summary: '',
    published: false
  },
  urlRoot: '/api/books'
});
```
This defines a basic book model with defaults for title, author, summary, and published status. The `urlRoot` property specifies the base URL for CRUD operations.

Next, we'll create a collection of books. A collection is just a group of models.
```javascript
// collections/Books.js
var Books = Backbone.Collection.extend({
  model: Book,
  url: '/api/books'
});
```
Here, we're telling Backbone that this collection should be made up of `Book` models, and that the base URL for fetching the collection is `/api/books`.

Now, let's move on to the views.
```javascript
// views/Book.js
var BookView = Backbone.View.extend({
  tagName: 'li',
  template: _.template('#book-template'),
  events: {
    'click .delete': 'removeBook'
  },
  render: function() {
    this.$el.html(this.template(this.model.toJSON()));
    return this;
  },
  removeBook: function() {
    this.model.destroy();
  }
});
```
In this view, we're specifying a `tagName` of `li` to wrap our book data in a list item. We're also defining a `template` property that will be used to render our book data. The `events` object specifies that when the `.delete` element is clicked, the `removeBook` method should be called. The `render` method is called when the view is rendered, and it sets the HTML of the view to the rendered template. Finally, the `removeBook` method destroys the book model.

Next, we'll create a view for the book list.
```javascript
// views/Books.js
var BooksView = Backbone.View.extend({
  tagName: 'ul',
  template: _.template('#books-template'),
  events: {},
  render: function() {
    var html = this.template({ books: this.collection.toJSON() });
    this.$el.html(html);
    this.collection.each(function(book) {
      var bookView = new BookView({ model: book });
      this.$el.append(bookView.render().el);
    }, this);
    return this;
  }
});
```
In this view, we're specifying a `tagName` of `ul` to wrap our book list in an unordered list. We're also defining a `template` property that will be used to render our book list. The `render` method is called when the view is rendered, and it sets the HTML of the view to the rendered template. It also creates a new `BookView` for each book in the collection and appends it to the list.

Now, let's move on to the router.
```javascript
// routers/BooksRouter.js
var BooksRouter = Backbone.Router.extend({
  routes: {
    '': 'index',
    'books/:id': 'show'
  },
  index: function() {
    var books = new Books();
    books.fetch({
      success: function(data) {
        var booksView = new BooksView({ collection: books });
        booksView.render();
        $('#app').html(booksView.el);
      }
    });
  },
  show: function(id) {
    var book = new Book({ id: id });
    book.fetch({
      success: function(data) {
        var bookView = new BookView({ model: book });
        bookView.render();
        $('#app').html(bookView.el);
      }
    });
  }
});
```
This router defines two routes: an empty route that will show the book list, and a route for showing a single book. When the `index` route is triggered, it will fetch the collection of books and render the book list view. When the `show` route is triggered, it will fetch the book with the specified ID and render the book view.

Now, let's talk about the API. We'll use PHP to create a simple RESTful API. Here's an example of how we can create a book:
```php
// api/books.php
<?[/INST]