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);

如果你使用的是PHP 5.3 >，这是目前为止最准确的计算绝对差值的方法:

$earlier = new DateTime("2010-07-06");
$later = new DateTime("2010-07-09");

$abs_diff = $later->diff($earlier)->format("%a"); //3

如果你需要一个相对的(带符号的)天数，可以用这个代替:

$earlier = new DateTime("2010-07-06");
$later = new DateTime("2010-07-09");

$pos_diff = $earlier->diff($later)->format("%r%a"); //3
$neg_diff = $later->diff($earlier)->format("%r%a"); //-3

更多关于php的DateInterval格式可以在这里找到:https://www.php.net/manual/en/dateinterval.format.php

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);

这个工作!

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

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

function howManyDays($startDate,$endDate) {

    $date1  = strtotime($startDate." 0:00:00");
    $date2  = strtotime($endDate." 23:59:59");
    $res    =  (int)(($date2-$date1)/86400);        

return $res;
} 

如果你有以秒为单位的时间(即unix时间戳)，那么你可以简单地减去时间并除以86400(秒/天)