bookstore.php

<?php
/**
 * Plugin Name: Bookstore
 * Description: A plugin to manage books
 * Version: 1.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly
}

add_action( 'init', 'bookstore_register_book_post_type' );
function bookstore_register_book_post_type() {
	$args = array(
		'labels'       => array(
			'name'          => 'Books',
			'singular_name' => 'Book',
			'menu_name'     => 'Books',
			'add_new'       => 'Add New Book',
			'add_new_item'  => 'Add New Book',
			'new_item'      => 'New Book',
			'edit_item'     => 'Edit Book',
			'view_item'     => 'View Book',
			'all_items'     => 'All Books',
		),
		'public'       => true,
		'has_archive'  => true,
		'show_in_rest' => true,
		'supports'     => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'custom-fields' ),
	);

	register_post_type( 'book', $args );

	// Add an isbn custom field to the book post type
	register_meta(
		'post',
		'isbn',
		array(
			'object_subtype' => 'book',
			'show_in_rest' => true,
			'single'       => true,
			'type'         => 'string',
		)
	);
}

add_action( 'init', 'bookstore_register_genre_taxonomy' );
function bookstore_register_genre_taxonomy() {
	$args = array(
		'labels'       => array(
			'name'          => 'Genres',
			'singular_name' => 'Genre',
			'edit_item'     => 'Edit Genre',
			'update_item'   => 'Update Genre',
			'add_new_item'  => 'Add New Genre',
			'new_item_name' => 'New Genre Name',
			'menu_name'     => 'Genre',
		),
		'hierarchical' => true,
		'rewrite'      => array( 'slug' => 'genre' ),
		'show_in_rest' => true,
	);
	register_taxonomy( 'genre', 'book', $args );
}

add_filter( 'postmeta_form_keys', 'bookstore_add_isbn_to_quick_edit', 10, 2 );
function bookstore_add_isbn_to_quick_edit( $keys, $post ) {
	if ( $post->post_type === 'book' ) {
		$keys[] = 'isbn';
	}
	return $keys;
}