- explode: documentation ( source)
<?php
$date1 = new DateTime('24 June 1940');
$date2 = new DateTime('now');
list($year1, $dayOfYear1) = explode(' ', $date1->format('Y z'));
list($year2, $dayOfYear2) = explode(' ', $date2->format('Y z'));
$age = $year1 - $year2 - ($dayOfYear1 < $dayOfYear2);
print $age;