1. Go to this page and download the library: Download sau/wp-settings-api library. Choose the download type require.
2. Extract the ZIP file and open the index.php.
3. Add this code to the index.php.
<?php
require_once('vendor/autoload.php');
/* Start to develop here. Best regards https://php-download.com/ */
sau / wp-settings-api example snippets
use Sau\WP\SettingsAPI\SettingsGroup;
$group_id='pages';
$group_title='Страницы';
$page_id='reading';
$setting_group = new SettingsGroup($group_id,$group_title,$page_id);