php常用的日期时间操作

//把当前日期时间以指定的格式转成字符串
$date_out=date ( 'Y-m-d H:i:s', time () );
//把时间字符串改成时间戳
$aab=strtotime($date_out);
//计算天数
     $NowTime = $proall['date'];
     $aab=strtotime($NowTime);
     $NowTime=date('Y-m-d',$aab);
     $NowTime2=date('Y-m-d',time());

     $day1 = $NowTime;
     $day2 = $NowTime2;
     $diff = diffBetweenTwoDays($day1, $day2);