这是可运行的代码

$date1 = date_create('2007-03-24');
$date2 = date_create('2009-06-26');
$diff1 = date_diff($date1,$date2);
$daysdiff = $diff1->format("%R%a");
$daysdiff = abs($daysdiff);

最好的做法是使用PHP的DateTime（和DateInterval）对象。每个日期都封装在DateTime对象中，然后可以在两者之间进行区别：

$first_date = new DateTime("2012-11-30 17:03:30");
$second_date = new DateTime("2012-12-21 00:00:00");

DateTime对象将接受strtotime（）的任何格式。如果需要更具体的日期格式，则可以使用DateTime:：createFromFormat（）创建DateTime对象。

两个对象实例化后，使用DateTime:：diff（）从另一个对象中减去一个对象。

$difference = $first_date->diff($second_date);

$difference现在保存一个包含差异信息的DateInterval对象。var_dump（）如下所示：

object(DateInterval)
  public 'y' => int 0
  public 'm' => int 0
  public 'd' => int 20
  public 'h' => int 6
  public 'i' => int 56
  public 's' => int 30
  public 'invert' => int 0
  public 'days' => int 20

要格式化DateInterval对象，我们需要检查每个值，如果值为0，则将其排除：

/**
 * Format an interval to show all existing components.
 * If the interval doesn't have a time component (years, months, etc)
 * That component won't be displayed.
 *
 * @param DateInterval $interval The interval
 *
 * @return string Formatted interval string.
 */
function format_interval(DateInterval $interval) {
    $result = "";
    if ($interval->y) { $result .= $interval->format("%y years "); }
    if ($interval->m) { $result .= $interval->format("%m months "); }
    if ($interval->d) { $result .= $interval->format("%d days "); }
    if ($interval->h) { $result .= $interval->format("%h hours "); }
    if ($interval->i) { $result .= $interval->format("%i minutes "); }
    if ($interval->s) { $result .= $interval->format("%s seconds "); }

    return $result;
}

现在剩下的就是调用$differenceDateInterval对象上的函数：

echo format_interval($difference);

我们得到了正确的结果：

20天6小时56分30秒

用于实现目标的完整代码：

/**
 * Format an interval to show all existing components.
 * If the interval doesn't have a time component (years, months, etc)
 * That component won't be displayed.
 *
 * @param DateInterval $interval The interval
 *
 * @return string Formatted interval string.
 */
function format_interval(DateInterval $interval) {
    $result = "";
    if ($interval->y) { $result .= $interval->format("%y years "); }
    if ($interval->m) { $result .= $interval->format("%m months "); }
    if ($interval->d) { $result .= $interval->format("%d days "); }
    if ($interval->h) { $result .= $interval->format("%h hours "); }
    if ($interval->i) { $result .= $interval->format("%i minutes "); }
    if ($interval->s) { $result .= $interval->format("%s seconds "); }

    return $result;
}

$first_date = new DateTime("2012-11-30 17:03:30");
$second_date = new DateTime("2012-12-21 00:00:00");

$difference = $first_date->diff($second_date);

echo format_interval($difference);

我建议使用DateTime和DateInterval对象。

$date1 = new DateTime("2007-03-24");
$date2 = new DateTime("2009-06-26");
$interval = $date1->diff($date2);
echo "difference " . $interval->y . " years, " . $interval->m." months, ".$interval->d." days "; 

// shows the total amount of days (not divided into years, months and days like above)
echo "difference " . $interval->days . " days ";

阅读更多php DateTime:：diff手册

根据手册：

从PHP 5.2.2开始，DateTime对象可以使用比较运算符进行比较。

$date1 = new DateTime("now");
$date2 = new DateTime("tomorrow");

var_dump($date1 == $date2); // bool(false)
var_dump($date1 < $date2);  // bool(true)
var_dump($date1 > $date2);  // bool(false)

这是我的职责。所需PHP>=5.3.4。它使用DateTime类。非常快，很快，可以区分两个日期，甚至所谓的“开始时间”。

if(function_exists('grk_Datetime_Since') === FALSE){
    function grk_Datetime_Since($From, $To='', $Prefix='', $Suffix=' ago', $Words=array()){
        #   Est-ce qu'on calcul jusqu'à un moment précis ? Probablement pas, on utilise maintenant
        if(empty($To) === TRUE){
            $To = time();
        }

        #   On va s'assurer que $From est numérique
        if(is_int($From) === FALSE){
            $From = strtotime($From);
        };

        #   On va s'assurer que $To est numérique
        if(is_int($To) === FALSE){
            $To = strtotime($To);
        }

        #   On a une erreur ?
        if($From === FALSE OR $From === -1 OR $To === FALSE OR $To === -1){
            return FALSE;
        }

        #   On va créer deux objets de date
        $From = new DateTime(@date('Y-m-d H:i:s', $From), new DateTimeZone('GMT'));
        $To   = new DateTime(@date('Y-m-d H:i:s', $To), new DateTimeZone('GMT'));

        #   On va calculer la différence entre $From et $To
        if(($Diff = $From->diff($To)) === FALSE){
            return FALSE;
        }

        #   On va merger le tableau des noms (par défaut, anglais)
        $Words = array_merge(array(
            'year'      => 'year',
            'years'     => 'years',
            'month'     => 'month',
            'months'    => 'months',
            'week'      => 'week',
            'weeks'     => 'weeks',
            'day'       => 'day',
            'days'      => 'days',
            'hour'      => 'hour',
            'hours'     => 'hours',
            'minute'    => 'minute',
            'minutes'   => 'minutes',
            'second'    => 'second',
            'seconds'   => 'seconds'
        ), $Words);

        #   On va créer la chaîne maintenant
        if($Diff->y > 1){
            $Text = $Diff->y.' '.$Words['years'];
        } elseif($Diff->y == 1){
            $Text = '1 '.$Words['year'];
        } elseif($Diff->m > 1){
            $Text = $Diff->m.' '.$Words['months'];
        } elseif($Diff->m == 1){
            $Text = '1 '.$Words['month'];
        } elseif($Diff->d > 7){
            $Text = ceil($Diff->d/7).' '.$Words['weeks'];
        } elseif($Diff->d == 7){
            $Text = '1 '.$Words['week'];
        } elseif($Diff->d > 1){
            $Text = $Diff->d.' '.$Words['days'];
        } elseif($Diff->d == 1){
            $Text = '1 '.$Words['day'];
        } elseif($Diff->h > 1){
            $Text = $Diff->h.' '.$Words['hours'];
        } elseif($Diff->h == 1){
            $Text = '1 '.$Words['hour'];
        } elseif($Diff->i > 1){
            $Text = $Diff->i.' '.$Words['minutes'];
        } elseif($Diff->i == 1){
            $Text = '1 '.$Words['minute'];
        } elseif($Diff->s > 1){
            $Text = $Diff->s.' '.$Words['seconds'];
        } else {
            $Text = '1 '.$Words['second'];
        }

        return $Prefix.$Text.$Suffix;
    }
}

我有一些简单的逻辑：

<?php
    per_days_diff('2011-12-12','2011-12-29')
    function per_days_diff($start_date, $end_date) {
        $per_days = 0;
        $noOfWeek = 0;
        $noOfWeekEnd = 0;
        $highSeason=array("7", "8");

        $current_date = strtotime($start_date);
        $current_date += (24 * 3600);
        $end_date = strtotime($end_date);

        $seassion = (in_array(date('m', $current_date), $highSeason))?"2":"1";

        $noOfdays = array('');

        while ($current_date <= $end_date) {
            if ($current_date <= $end_date) {
                $date = date('N', $current_date);
                array_push($noOfdays,$date);
                $current_date = strtotime('+1 day', $current_date);
            }
        }

        $finalDays = array_shift($noOfdays);
        //print_r($noOfdays);
        $weekFirst = array("week"=>array(),"weekEnd"=>array());
        for($i = 0; $i < count($noOfdays); $i++)
        {
            if ($noOfdays[$i] == 1)
            {
                //echo "This is week";
                //echo "<br/>";
                if($noOfdays[$i+6]==7)
                {
                    $noOfWeek++;
                    $i=$i+6;
                }
                else
                {
                    $per_days++;
                }
                //array_push($weekFirst["week"],$day);
            }
            else if($noOfdays[$i]==5)
            {
                //echo "This is weekend";
                //echo "<br/>";
                if($noOfdays[$i+2] ==7)
                {
                    $noOfWeekEnd++;
                    $i = $i+2;
                }
                else
                {
                    $per_days++;
                }
                //echo "After weekend value:- ".$i;
                //echo "<br/>";
            }
            else
            {
                $per_days++;
            }
        }

        /*echo $noOfWeek;
          echo "<br/>";
          echo $noOfWeekEnd;
          echo "<br/>";
          print_r($per_days);
          echo "<br/>";
          print_r($weekFirst);
        */

        $duration = array("weeks"=>$noOfWeek, "weekends"=>$noOfWeekEnd, "perDay"=>$per_days, "seassion"=>$seassion);
        return $duration;
      ?>

我不知道你是否在使用PHP框架，但很多PHP框架都有日期/时间库和助手来帮助你避免重新发明轮子。

例如，CodeIgniter具有timespan（）函数。只需输入两个Unix时间戳，就会自动生成如下结果：

1 Year, 10 Months, 2 Weeks, 5 Days, 10 Hours, 16 Minutes

http://codeigniter.com/user_guide/helpers/date_helper.html