- explode: documentation ( source)
<?php
$from = new DateTime('24 June 1940');
$till = new DateTime('now');
list($fromYear, $fromDay) = explode(' ', $from->format('Y z'));
list($tillYear, $tillDay) = explode(' ', $till->format('Y z'));
$age = $tillYear - $fromYear - ($tillDay < $fromDay);
print $age;