<?
/**
* 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<br>";
echo $d1."的10天前是".date("Y-m-d",dateadd("d",-10,$d1))."<br>";
$d3 = date("Y/m/d H:i:s");
echo "现在是".$d3."距离2002/2/12 12:59:59还有".datediff("s",$d3,"2002/2/12 12:59:59")."秒<br>";

?>