DateTime::diff unexpected results

问题

I have the following calculation, which I expect to return 0. However it returns 1 on many systems I have access to:

Ubuntu 16.04 server (wrong)

php -v
PHP 7.0.22-0ubuntu0.16.04.1 (cli) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
    with Zend OPcache v7.0.22-0ubuntu0.16.04.1, Copyright (c) 1999-
2017, by Zend Technologies

echo "<?php echo DateTime::createFromFormat('Y-m-d H:i:s', '2017-12-01 00:00:00')->diff(DateTime::createFromFormat('Y-m-d H:i:s', '2017-12-31 23:59:59' ))->format('%m');"|php
1

PHP 7.1 from deb.sury.org with Xdebug (wrong)

php -v
PHP 7.1.6-1~ubuntu16.04.1+deb.sury.org+1 (cli) (built: Jun  9 2017 
08:26:34) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies
    with Zend OPcache v7.1.6-1~ubuntu16.04.1+deb.sury.org+1, Copyright 
(c) 1999-2017, by Zend Technologies
    with Xdebug v2.5.4, Copyright (c) 2002-2017, by Derick Rethans

echo "<?php echo DateTime::createFromFormat('Y-m-d H:i:s', '2017-12-01 00:00:00')->diff(DateTime::createFromFormat('Y-m-d H:i:s', '2017-12-31 23:59:59' ))->format('%m');"|php
1

phpfiddle.org

--> returns 0 as expected

The timezones of the date are the same

回答1:

A note from DateInterval::format:

The DateInterval::format() method does not recalculate carry over points in time strings nor in date segments. This is expected because it is not possible to overflow values like "32 days" which could be interpreted as anything from "1 month and 4 days" to "1 month and 1 day".

So one has to recalculate carry over points. Below is the relevant code from DateInterval::format:

class DateIntervalEnhanced extends DateInterval {
    public function recalculate() {
        $from = new DateTime;
        $to = clone $from;
        $to->add($this);
        $diff = $from->diff($to);
        foreach ($diff as $k => $v) $this->$k = $v;
        return $this;
    }
}

A utility function:

function myFormatter($d1, $d2, $format) {
    $diff = strtotime($d1) - strtotime($d2);
    $df = abs($diff);
    $di = new DateIntervalEnhanced("PT${df}S");
    $di->invert = $diff < 0;
    return $di->recalculate()->format($format);
}

echo myFormatter("2017-12-31 23:59:59", "2017-12-01 00:00:00", "%m");

DEMO

Link to a post you might wanna read

来源：https://stackoverflow.com/questions/48435169/datetimediff-unexpected-results

标签

php

datetime

dateinterval