Create a WordPress custom post type

In your theme’s functions.php file, insert the following code:
  
 // Create out post type
    add_action( 'init', 'create_post_type' );
    function create_post_type() {
            $args = array(
            'labels' => post_type_labels( 'Book' ),
            'public' => true,
            'publicly_queryable' => true,
            'show_ui' => true,
            'show_in_menu' => true,
            'query_var' => true,
            'rewrite' => true,
            'capability_type' => 'post',
            'has_archive' => true,
            'hierarchical' => false,
            'menu_position' => null,
            'supports' => array('title',
                'editor',
                'author',
                'thumbnail',
                'excerpt',
                'comments'
            )
        );
   
            register_post_type( 'book', $args );
    }
   
    // A helper function for generating the labels
    function post_type_labels( $singular, $plural = '' )
    {
        if( $plural == '') $plural = $singular .'s';
     
        return array(
            'name' => _x( $plural, 'post type general name' ),
            'singular_name' => _x( $singular, 'post type singular name' ),
            'add_new' => __( 'Add New' ),
            'add_new_item' => __( 'Add New '. $singular ),
            'edit_item' => __( 'Edit '. $singular ),
            'new_item' => __( 'New '. $singular ),
            'view_item' => __( 'View '. $singular ),
            'search_items' => __( 'Search '. $plural ),
            'not_found' =>  __( 'No '. $plural .' found' ),
            'not_found_in_trash' => __( 'No '. $plural .' found in Trash' ),
            'parent_item_colon' => ''
        );
    }
   
    //add filter to ensure the text Book, or book, is displayed when user updates a book
    add_filter('post_updated_messages', 'post_type_updated_messages');
    function post_type_updated_messages( $messages ) {
            global $post, $post_ID;
   
            $messages['book'] = array(
                    0 => '', // Unused. Messages start at index 1.
                    1 => sprintf( __('Book updated. <a href="%s">View book</a>'), esc_url( get_permalink($post_ID) ) ),
                    2 => __('Custom field updated.'),
                    3 => __('Custom field deleted.'),
                    4 => __('Book updated.'),
                    /* translators: %s: date and time of the revision */
                    5 => isset($_GET['revision']) ? sprintf( __('Book restored to revision from %s'), wp_post_revision_title( (int) $_GET['revision'], false ) ) : false,
                    6 => sprintf( __('Book published. <a href="%s">View book</a>'), esc_url( get_permalink($post_ID) ) ),
                    7 => __('Book saved.'),
                    8 => sprintf( __('Book submitted. <a target="_blank" href="%s">Preview book</a>'), esc_url( add_query_arg( 'preview', 'true', get_permalink($post_ID) ) ) ),
                    9 => sprintf( __('Book scheduled for: <strong>%1$s</strong>. <a target="_blank" href="%2$s">Preview book</a>'),
                    // translators: Publish box date format, see php.net/date
                    date_i18n( __( 'M j, Y @ G:i' ), strtotime( $post->post_date ) ), esc_url( get_permalink($post_ID) ) ),
                    10 => sprintf( __('Book draft updated. <a target="_blank" href="%s">Preview book</a>'), esc_url( add_query_arg( 'preview', 'true', get_permalink($post_ID) ) ) ),
            );
   
            return $messages;
    }