使用这个:)

$days = (strtotime($endDate) - strtotime($startDate)) / (60 * 60 * 24);
print $days;

现在起作用了

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。

如果你正在使用MySql

function daysSince($date, $date2){
$q = "SELECT DATEDIFF('$date','$date2') AS days;";
$result = execQ($q);
$row = mysql_fetch_array($result,MYSQL_BOTH);
return ($row[0]);

}

function execQ($q){
$result = mysql_query( $q);
if(!$result){echo ('Database error execQ' . mysql_error());echo $q;}    
return $result;

}

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);
}

你可以通过简单的方法找到约会对象

<?php
$start  = date_create('1988-08-10');
$end    = date_create(); // Current time and date
$diff   = date_diff( $start, $end );

echo 'The difference is ';
echo  $diff->y . ' years, ';
echo  $diff->m . ' months, ';
echo  $diff->d . ' days, ';
echo  $diff->h . ' hours, ';
echo  $diff->i . ' minutes, ';
echo  $diff->s . ' seconds';
// Output: The difference is 28 years, 5 months, 19 days, 20 hours, 34 minutes, 36 seconds

echo 'The difference in days : ' . $diff->days;
// Output: The difference in days : 10398

使用这个简单的函数。声明函数

<?php
function dateDiff($firstDate,$secondDate){
    $firstDate = strtotime($firstDate);
    $secondDate = strtotime($secondDate);

    $datediff = $firstDate - $secondDate;
    $output = round($datediff / (60 * 60 * 24));
    return $output;
}
?>

像这样调用这个函数

<?php
    echo dateDiff("2018-01-01","2018-12-31");    

// OR

    $firstDate = "2018-01-01";
    $secondDate = "2018-01-01";
    echo dateDiff($firstDate,$secondDate);    
?>