Obter a diferença em semanas, dias, horas, minutos e segundos entre duas datas

<?
// 7:32:56 pm on May 10, 1965
$epoch_1 = mktime(19,32,56,5,10,1965);
// 4:29:11 am on November 20, 1962
$epoch_2 = mktime(4,29,11,11,20,1962);
$diff_seconds = $epoch_1 - $epoch_2;
$diff_weeks = floor($diff_seconds/604800);
$diff_seconds -= $diff_weeks * 604800;
$diff_days = floor($diff_seconds/86400);
$diff_seconds -= $diff_days * 86400;
$diff_hours = floor($diff_seconds/3600);
$diff_seconds -= $diff_hours * 3600;
$diff_minutes = floor($diff_seconds/60);
$diff_seconds -= $diff_minutes * 60;
print "As duas datas têm $diff_weeks semanas, 
   $diff_days dias, ";
print "$diff_hours horas, $diff_minutes minutos 
   e $diff_seconds ";
print "segundos de diferença.";
?>