WPプラグイン開発入門 (4)メタボックス

<?php
/**
 * Dashboard Right Now Plus
 *
 * @package           DashboardRightNowPlus
 *
 * @wordpress-plugin
 * Plugin Name:       Dashboard Right Now Plus
 * Plugin URI:        https://gist.github.com/web83info/5747ac715e4544b408e91e2ec034ab05/
 * Description:       Add custom post type to "Right Now" meta box on WordPress dashboard
 * Version:           1.0.0
 * Requires at least: 6.4
 * Requires PHP:      7.2
 * Author:            web83info
 * Author URI:        https://labs.web83.info/
 * License:           GPL v2 or later
 * License URI:       https://www.gnu.org/licenses/gpl-2.0.html
 */

/**
 * カスタム投稿タイプdrnp-mycpt-a, drnp-mycpt-b を追加
 *
 * @return void
 */
function drnp_add_my_custom_post_type() {
	$custom_post_types = array(
		'drnp-mycpt-a' => array(
			'type' => 'drnp-mycpt-a',
			'name' => 'マイCPT-A',
		),
		'drnp-mycpt-b' => array(
			'type' => 'drnp-mycpt-b',
			'name' => 'マイCPT-B',
		),
	);
	foreach ( $custom_post_types as $custom_post_type ) {
		register_post_type(
			$custom_post_type['type'],
			array(
				'labels' => array(
					'name'          => $custom_post_type['name'],
					'singular_name' => $custom_post_type['name'],
				),
				'public' => true,
			)
		);

		if ( 0 === wp_count_posts( $custom_post_type['type'] )->publish ) {
			for ( $i = 1; $i <= 3; $i++ ) {
				wp_insert_post(
					array(
						'post_type'   => $custom_post_type['type'],
						'post_title'  => $custom_post_type['name'] . ' 記事 #' . $i,
						'post_status' => 'publish',
					)
				);
			}
		}
	}
}
add_action( 'init', 'drnp_add_my_custom_post_type' );

/**
 * アンインストール時にカスタム投稿タイプdrnp-mycpt-a, drnp-mycpt-b の記事を削除
 *
 * @return void
 */
function drnp_uninstall_my_custom_post_type() {
	$args  = array(
		'post_type'   => array(
			'drnp-mycpt-a',
			'drnp-mycpt-b',
		),
		'numberposts' => -1,
	);
	$posts = get_posts( $args );

	foreach ( $posts as $post ) {
		wp_delete_post( $post->ID );
	}
}
register_uninstall_hook( __FILE__, 'drnp_uninstall_my_custom_post_type' );

/**
 * 概要メタボックスにカスタム投稿タイプの件数を表示
 *
 * @param array $elements 追加表示させる内容.
 * @return array 追加表示させる内容.
 */
function drnp_add_my_custom_post_type_to_right_now( $elements ) {
	foreach ( array( 'drnp-mycpt-a', 'drnp-mycpt-b' ) as $post_type ) {
		$num_posts = wp_count_posts( $post_type );
		if ( $num_posts && $num_posts->publish ) {
			$post_type_object = get_post_type_object( $post_type );
			$text             = sprintf( '%s件の%s', number_format_i18n( $num_posts->publish ), $post_type_object->labels->name );
			if ( $post_type_object && current_user_can( $post_type_object->cap->edit_posts ) ) {
				$elements[] = sprintf( '<a class="%1$s-count" href="edit.php?post_type=%1$s">%2$s</a>', esc_html( $post_type ), esc_html( $text ) );
			} else {
				$elements[] = sprintf( '<span class="%1$s-count">%2$s</span></li>', esc_html( $post_type ), esc_html( $text ) );
			}
		}
	}
	return $elements;
}
add_filter( 'dashboard_glance_items', 'drnp_add_my_custom_post_type_to_right_now' );