- date_add: documentation ( source)
- date_create: documentation ( source)
- date_interval_create_from_date_string: documentation ( source)
- date_format: documentation ( source)
<?php
$date = date_create('2000-01-01');
echo $date;
date_add($date, date_interval_create_from_date_string('10 days'));
echo date_format($date, 'Y-m-d');