function get_daydiff($end_date,$today)
{
    if($today=='')
    {
        $today=date('Y-m-d');
    }
    $str = floor(strtotime($end_date)/(60*60*24)) - floor(strtotime($today)/(60*60*24));
    return $str;
}
$d1 = "2018-12-31";
$d2 = "2018-06-06";
echo get_daydiff($d1, $d2);

使用这个:)

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

现在起作用了

这是我的改进版本，显示1年2月25天(s)，如果通过第二个参数。

class App_Sandbox_String_Util {
    /**
     * Usage: App_Sandbox_String_Util::getDateDiff();
     * @param int $your_date timestamp
     * @param bool $hr human readable. e.g. 1 year(s) 2 day(s)
     * @see http://stackoverflow.com/questions/2040560/finding-the-number-of-days-between-two-dates
     * @see http://qSandbox.com
     */
    static public function getDateDiff($your_date, $hr = 0) {
        $now = time(); // or your date as well
        $datediff = $now - $your_date;
        $days = floor( $datediff / ( 3600 * 24 ) );

        $label = '';

        if ($hr) {
            if ($days >= 365) { // over a year
                $years = floor($days / 365);
                $label .= $years . ' Year(s)';
                $days -= 365 * $years;
            }

            if ($days) {
                $months = floor( $days / 30 );
                $label .= ' ' . $months . ' Month(s)';
                $days -= 30 * $months;
            }

            if ($days) {
                $label .= ' ' . $days . ' day(s)';
            }
        } else {
            $label = $days;
        }

        return $label;
    }
}

面向对象的风格:

$datetime1 = new DateTime('2009-10-11');
$datetime2 = new DateTime('2009-10-13');
$interval = $datetime1->diff($datetime2);
echo $interval->format('%R%a days');

程序上的风格:

$datetime1 = date_create('2009-10-11');
$datetime2 = date_create('2009-10-13');
$interval = date_diff($datetime1, $datetime2);
echo $interval->format('%R%a days');

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。

    // 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";