$early_start_date = date2sql($_POST['early_leave_date']);


$date = new DateTime($early_start_date);
$date->modify('+1 day');


$date_a = new DateTime($early_start_date . ' ' . $_POST['start_hr'] . ':' . $_POST['start_mm']);
$date_b = new DateTime($date->format('Y-m-d') . ' ' . $_POST['end_hr'] . ':' . $_POST['end_mm']);

$interval = date_diff($date_a, $date_b);


$time = $interval->format('%h:%i');
$parsed = date_parse($time);
$seconds = $parsed['hour'] * 3600 + $parsed['minute'] * 60;
//        display_error($seconds);

$second3 = $employee_information['shift'] * 60 * 60;

if ($second3 < $seconds)
    display_error(_('Leave time can not be greater than shift time.Please try again........'));
    set_focus('start_hr');
    set_focus('end_hr');
    return FALSE;
}

    // Change this to the day in the future
$day = 15;

// Change this to the month in the future
$month = 11;

// Change this to the year in the future
$year = 2012;

// $days is the number of days between now and the date in the future
$days = (int)((mktime (0,0,0,$month,$day,$year) - time(void))/86400);

echo "There are $days days until $day/$month/$year";

计算两个日期的差值:

$date1=date_create("2013-03-15");
$date2=date_create("2013-12-12");

$diff=date_diff($date1,$date2);

echo $diff->format("%R%a days");

输出: + 272天

函数的作用是:返回两个DateTime对象之间的差值。

$start = '2013-09-08';
$end = '2013-09-15';
$diff = (strtotime($end)- strtotime($start))/24/3600; 
echo $diff;

看看所有的答案，我写了一个通用函数，适用于所有的PHP版本。

if(!function_exists('date_between')) :
    function date_between($date_start, $date_end)
    {
        if(!$date_start || !$date_end) return 0;

        if( class_exists('DateTime') )
        {
            $date_start = new DateTime( $date_start );
            $date_end   = new DateTime( $date_end );
            return $date_end->diff($date_start)->format('%a');
        }
        else
        {           
            return abs( round( ( strtotime($date_start) - strtotime($date_end) ) / 86400 ) );
        }
    }
endif;

一般来说，我使用“DateTime”来查找两个日期之间的天数。但如果出于某种原因，一些服务器设置没有启用'DateTime'，它将使用'strtotime()'简单(但不安全)计算。

这个工作!

$start = strtotime('2010-01-25');
$end = strtotime('2010-02-20');

$days_between = ceil(abs($end - $start) / 86400);