WordPressで記事を公開する際の著者名をカスタマイズする方法を伝授

<?php
/*
Plugin Name: Custom Author
Plugin URI: https://www.ixiqin.com/2018/06/wordpress-custom-author-plugin/
Description: Custom Author Plugin
Version: 1.0
Author: Bestony
Author URI: https://www.ixiqin.com/
License: GPL2
License URI: https://www.gnu.org/licenses/gpl-2.0.html
 */
/* Copyright 2018 Bestony (email : [email protected])
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
this program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation, Inc.
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */


add_action('post_submitbox_misc_actions', 'cus_author_createCustomField');
add_action('save_post', 'cus_author_saveCustomField');
/** Create a checkBox */
function cus_author_createCustomField() {
	$post_id = get_the_ID();
	if (get_post_type($post_id) ! = 'post') {
		return;
	}
	/**
	 * Extract the existing value
	 * @var boolean
	 */
	$value = get_post_meta($post_id, '_custom_author_name', true);
	/**
	 * Add nonce security handling
	 */
	wp_nonce_field('custom_author_nonce' , 'custom_author_nonce');
	? >
    <div class="misc-pub-section misc-pub-section-last dashicons-before dashicons-admin-users">
        <label><b>Author:</b><input type="text" value="<?php echo $value ? >" name="_custom_author_name" /></label>
    </div>
    <?php   
}
/**
 * Save configuration information
 * @param int $post_id ID of the article
 */
function cus_author_saveCustomField($post_id) {
	/**
	 * Auto-save is not processed
	 */
	if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
		return;
	}
	/**
	 * nonce information is not processed correctly
	 */
	if (
		!isset($_POST['custom_author_nonce']) ||
		!wp_verify_nonce($_POST['custom_author_nonce'], 'custom_author_nonce')
	) {
		return;
	}
	/**
	 * User does not have the right to edit the article without processing
	 */
	if (!current_user_can('edit_post', $post_id)) {
		return;
	}
	/**
	 * Update if this item exists
	 */
	if (isset($_POST['_custom_author_name'])) {
		update_post_meta($post_id, '_custom_author_name', sanitize_text_field($_POST['_custom_author_name']));
	} else {
		/**
		 * Delete if it doesn't exist
		 */
		delete_post_meta($post_id, '_custom_author_name');
	}
}

add_filter('the_author','cus_author_the_author');
function cus_author_the_author($author){
    $custom_author = get_post_meta(get_the_ID(), '_custom_author_name');
    if ($custom_author) {
		return $custom_author[0];
	} else {
		return $author;
	}
}