string date ( string format [, int timestamp] ) //其中timestamp爲可選，默認值爲time();
date("1"); //Monday
date("m.d.y"); //12.21.09
date("m.d.Y");//12.21.2009
$tomorrow = mktime(0, 0, 0, date("m") , date("d")+1, date("Y"));
$lastmonth = mktime(0, 0, 0, date("m")-1, date("d"), date("Y"));
$nextyear = mktime(0, 0, 0, date("m"), date("d"), date("Y")+1);