/**
* 求两个日期之间相差的天数
* (针对1970年1月1日之后，求之前可以采用泰勒公式)
* @param string $start_day
* @param string $end_day
* @return number
*/
function get_daynumbers($start_day, $end_day)
{
    $second1 = strtotime($start_day);
$second2 = strtotime($end_day);
if ($second1 < $second2)
{
    $tmp = $second2;
$second2 = $second1;
$second1 = $tmp;
}

return ($second1 - $second2) / 86400;
}


$start_day = "2019-01-01";
$end_day = date("Y-m-d");

$num = get_daynumbers($start_day, $end_day);

本文地址：https://www.phpicu.com/article.php?id=57