PHP日期处理函数

<?php/* * author wuhan syspro zhangchao * date 2010/12/23 */// next dayfunction next_day($theday){if(!$theday){$theday=date(DATE_W3C);}return next_days($theday,1);}// pre dayfunction pre_day($theday){if(!$theday){$theday=date(DATE_W3C);}return next_days($theday,-1);}// next daysfunction next_days($theday,$incr){if(!$theday){$theday=date(DATE_W3C);}if(!$incr){$incr=1;}$nextday=strtotime($theday)+24*60*60*$incr;$nextday=date(DATE_W3C,$nextday);return $nextday;}// days between two datefunction interval_days($firstday,$lastday){if(!$firstday){$firstday=date(DATE_W3C);}if(!$lastday){$lastday=date(DATE_W3C);}$firstday=strtotime($firstday);$lastday=strtotime($lastday);$days=($lastday-$firstday)/60/60/24;return $days;}// first dayfunction first_day($theday){if(!$theday){$theday=date(DATE_W3C);}$firstday = date('Y-m-01', strtotime($theday)); return $firstday;}// last dayfunction last_day($theday){if(!$theday){$theday=date(DATE_W3C);}$firstday=first_day($theday);$lastday = date('Y-m-d', strtotime("$firstday +1 month -1 day")); return $lastday;}?>