Sample system plugin

my_plugin.php

<?php

/**
 * @copyright   Copyright (C) 2023 Joe Public. All rights reserved
 * @license     GNU General Public License version 2 or later
 */
defined('JPATH_BASE') or die;

use Joomla\CMS\Factory;
use Joomla\CMS\Plugin\CMSPlugin;

class PlgSystemMy_Plugin extends CMSPlugin
{
    public function onContentAfterSave($context, $article, $isNew): void
    {
        // Check we are handling the frontend edit form.
        if ($context !== 'com_content.form') {
            return;
        }
      
        // Check this is a new article.
        if (!$isNew) {
            return;
        }
      
        $app = Factory::getApplication();
    }
}