1. Go to this page and download the library: Download webtoucher/calendar 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/ */
webtoucher / calendar example snippets
$calendar = new Calendar(new Schedule('ru'));
$calendar = new Calendar(new Schedule('/var/www/my-site/rules/pl'));
echo $calendar->calendarToWorkingDays(new \DateTime('2016-02-24'), new \DateTime('2016-02-29')); // 3
echo $calendar->calendarToWorkingDays(new \DateTime('2016-02-29'), new \DateTime('2016-02-24')); // -3