PHP 日期时间函数 mktime()

<?php
   $lastday = mktime(0, 0, 0, 3, 0, 2010);
   echo strftime("Last day in Feb 2010 is: %dn", $lastday);

   $lastday = mktime(0, 0, 0, 4, -31, 2010);
   echo strftime("Last day in Feb 2010 is: %d", $lastday);
?>