Install jYProExtra in insall script

install_jyproextra.php

<?php

defined('_JEXEC') or die;

use Joomla\CMS\Factory;
use Joomla\CMS\Installer\Installer;
use Joomla\CMS\Installer\InstallerAdapter;
use Joomla\CMS\Installer\InstallerHelper;
use Joomla\CMS\Language\Text;
use Joomla\CMS\Plugin\PluginHelper;

class type_nameInstallerScript
{
	/**
	 * Runs right after any installation action.
	 *
	 * @param   string            $type    Type of PostFlight action.
	 * @param   InstallerAdapter  $parent  Parent object calling object.
	 *
	 * @throws  Exception
	 *
	 * @return  boolean True on success, false on failure.
	 *
	 * @since  __DEPLOY_VERSION__
	 */
	function postflight($type, $parent)
	{
		// Install jYProExtra
		if (!$this->installJYProExtra())
		{
			Factory::getApplication()->enqueueMessage(Text::_('ERROR_TEXT'), 'error');

			return false;
		}

		return true;
	}

	/**
	 *
	 * Method to check jYProExtra plugin and install if need.
	 *
	 * @throws  Exception
	 *
	 * @return  boolean  True on success, false on failure.
	 *
	 * @since  __DEPLOY_VERSION__
	 */
	protected function installJYProExtra()
	{
		if (!PluginHelper::getPlugin('system', 'jyproextra'))
		{
			// Download the package at the URL given
			if (!$p_file = InstallerHelper::downloadPackage(
				'https://www.septdir.com/solutions/download?element=plg_system_jyproextra'))
			{
				return false;
			}

			// Unpack the downloaded package file
			if (!$package = InstallerHelper::unpack(Factory::getConfig()->get('tmp_path') . '/' . $p_file, true))
			{
				return false;
			}

			// Check type
			if (!$package['type'])
			{
				InstallerHelper::cleanupInstall($package['packagefile'], $package['extractdir']);

				return false;
			}

			// Get an installer instance
			$installer = Installer::getInstance();
			$installer->setPath('source', $package['dir']);
			if (!$installer->findManifest())
			{
				InstallerHelper::cleanupInstall($package['packagefile'], $package['extractdir']);

				return false;
			}

			// Install the package
			if (!$installer->install($package['dir']))
			{
				InstallerHelper::cleanupInstall($package['packagefile'], $package['extractdir']);

				return false;
			}

			// CleanUp install
			InstallerHelper::cleanupInstall($package['packagefile'], $package['extractdir']);
		}
		
		return true;
	}
}