/**
* 转换为UNIX时间戳
*/
function gettime($d) {
if(is_numeric($d))
return $d;
else {
if(! is_string($d)) return 0;
if(ereg(":",$d)) {
$buf = split(" +",$d);
$year = split("[-/]",$buf[0]);
$hour = split(":",$buf[1]);
if(eregi("pm",$buf[2]))
$hour[0] += 12;
return mktime($hour[0],$hour[1],$hour[2],$year[1],$year[2],$year[0]);
}else {
$year = split("[-/]",$d);
return mktime(0,0,0,$year[1],$year[2],$year[0]);
}
}
}

/**
*
* DateAdd(interval,number,date)
* 返回已添加指定时间间隔的日期。
* Inetrval为表示要添加的时间间隔字符串表达式，例如分或天
* number为表示要添加的时间间隔的个数的数值表达式
* Date表示日期
*
* Interval(时间间隔字符串表达式)可以是以下任意值:
* yyyy year年
* q Quarter季度
* m Month月
* y Day of year一年的数
* d Day天
* w Weekday一周的天数
* ww Week of year周
* h Hour小时
* n Minute分
* s Second秒
* w、y和d的作用是完全一样的，即在目前的日期上加一天，q加3个月，ww加7天。
*/
function DateAdd($interval, $number, $date) {
$date = gettime($date);
$date_time_array = getdate($date);
$hours = $date_time_array["hours"];
$minutes = $date_time_array["minutes"];
$seconds = $date_time_array["seconds"];
$month = $date_time_array["mon"];
$day = $date_time_array["mday"];
$year = $date_time_array["year"];
switch ($interval) {
case "yyyy": $year +=$number; break;
case "q": $month +=($number*3); break;
case "m": $month +=$number; break;
case "y":
case "d":
case "w": $day+=$number; break;
case "ww": $day+=($number*7); break;
case "h": $hours+=$number; break;
case "n": $minutes+=$number; break;
case "s": $seconds+=$number; break;
}
$timestamp = mktime($hours ,$minutes, $seconds,$month ,$day, $year);
return $timestamp;
}

/**
* DateDiff(interval,date1,date2)
* 返回两个日期之间的时间间隔
* intervals(时间间隔字符串表达式)可以是以下任意值:
* w 周
* d 天
* h 小时
* n 分钟
* s 秒
*/
function DateDiff ($interval, $date1,$date2) {
// 得到两日期之间间隔的秒数
$timedifference = gettime($date2) - gettime($date1);
switch ($interval) {
case "w": $retval = bcdiv($timedifference ,604800); break;
case "d": $retval = bcdiv( $timedifference,86400); break;
case "h": $retval = bcdiv ($timedifference,3600); break;
case "n": $retval = bcdiv( $timedifference,60); break;
case "s": $retval = $timedifference; break;
}
return $retval;
}
?>
// 测试例
$d1 = "2002-01-11";
$d2 = date("Y-m-d",dateadd("d",15,$d1));
echo $d1."的". datediff("d",$d1,$d2)."天后是$d2
";
echo $d1."的10天前是".date("Y-m-d",dateadd("d",-10,$d1))."
";
$d3 = date("Y/m/d H:i:s");
echo "现在是".$d3."距离2002/2/12 12:59:59还有".datediff("s",$d3,"2002/2/12 12:59:59")."秒
";
?>