<?php
ini_set('date.timezone', 'Europe/Lisbon');
$cal = IntlCalendar::fromDateTime('2013-02-15');
var_dump($cal->getActualMaximum(IntlCalendar::FIELD_DAY_OF_MONTH)); //28
$cal->add(IntlCalendar::FIELD_EXTENDED_YEAR, -1);
var_dump($cal->getActualMaximum(IntlCalendar::FIELD_DAY_OF_MONTH)); //29