这段代码为我工作，并用PHP 8版本测试:

function numberOfDays($startDate, $endDate) 
{
    //1) converting dates to timestamps
     $startSeconds = strtotime($startDate);
     $endSeconds = strtotime($endDate);
   
    //2) Calculating the difference in timestamps
    $diffSeconds = $startSeconds  - $endSeconds;
     
    
    //3) converting timestamps to days
    $days=round($diffSeconds / 86400);
    
      /*  note :
          1 day = 24 hours 
          24 * 60 * 60 = 86400 seconds
      */
   
    //4) printing the number of days
    printf("Difference between two dates: ". abs($days) . " Days ");
    
    return abs($days);
}

易于使用date_diff

$from=date_create(date('Y-m-d'));
$to=date_create("2013-03-15");
$diff=date_diff($to,$from);
print_r($diff);
echo $diff->format('%R%a days');

详见:https://blog.devgenius.io/how-to-find-the-number-of-days-between-two-dates-in-php-1404748b1e84

将日期转换为unix时间戳，然后从另一个时间戳中减去一个日期。这将得到以秒为单位的差值，然后除以86400(一天中的秒数)，得到该范围内的大约天数。

如果你的日期格式为25.1.2010,01/25/2010或2010-01-25，你可以使用strtotime函数:

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

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

使用ceil将天数四舍五入到下一个全天。如果您希望获得这两个日期之间的完整天数，则使用floor。

如果日期已经是unix时间戳格式，则可以跳过转换，只执行$days_between部分。对于更奇特的日期格式，您可能必须进行一些自定义解析以使其正确。

这段代码为我工作，并用PHP 8版本测试:

function numberOfDays($startDate, $endDate) 
{
    //1) converting dates to timestamps
     $startSeconds = strtotime($startDate);
     $endSeconds = strtotime($endDate);
   
    //2) Calculating the difference in timestamps
    $diffSeconds = $startSeconds  - $endSeconds;
     
    
    //3) converting timestamps to days
    $days=round($diffSeconds / 86400);
    
      /*  note :
          1 day = 24 hours 
          24 * 60 * 60 = 86400 seconds
      */
   
    //4) printing the number of days
    printf("Difference between two dates: ". abs($days) . " Days ");
    
    return abs($days);
}

从PHP 5.3及以上版本开始，添加了新的日期/时间函数来获得不同:

$datetime1 = new DateTime("2010-06-20");

$datetime2 = new DateTime("2011-06-22");

$difference = $datetime1->diff($datetime2);

echo 'Difference: '.$difference->y.' years, ' 
                   .$difference->m.' months, ' 
                   .$difference->d.' days';

print_r($difference);

结果如下:

Difference: 1 years, 0 months, 2 days

DateInterval Object
(
    [y] => 1
    [m] => 0
    [d] => 2
    [h] => 0
    [i] => 0
    [s] => 0
    [invert] => 0
    [days] => 367
)

希望能有所帮助!

<?php
$date1=date_create("2013-03-15");
$date2=date_create("2013-12-12");
$diff=date_diff($date1,$date2);
echo $diff->format("%R%a days");
?>

上面的代码用的很简单。谢谢。