PHP DateTime::修改加减月份 [英] PHP DateTime::modify adding and subtracting months

问题描述

我一直在使用 DateTime 类 并且最近在添加月份时遇到了我认为的错误.经过一番研究，它似乎不是一个错误，而是按预期工作.根据此处的文档:

<块引用>

示例#2 添加或添加时要小心减去月份

modify('+1 个月');echo $date->format('Y-m-d') ."
";$date->modify('+1 个月');echo $date->format('Y-m-d') ."
";?>

<块引用>

上面的例子会输出:2001-01-312001-03-03

谁能证明为什么这不被视为错误?

此外，有没有人有任何优雅的解决方案来纠正问题并使其 +1 个月按预期工作而不是按预期工作?

解决方案

为什么它不是错误:

当前的行为是正确的.以下发生在内部:

1. +1 month 将月份数(原为 1)加 1.这使得日期 2010-02-31.

2. 第二个月(二月)在 2010 年只有 28 天，因此 PHP 会通过继续计算从 2 月 1 日开始的天数来自动更正这一点.然后你会在 3 月 3 日结束.

如何得到你想要的:

要得到你想要的东西是:手动检查下个月.然后加上下个月的天数.

我希望你可以自己编写代码.我只是在提供该做什么.

PHP 5.3 方式:

要获得正确的行为，您可以使用 PHP 5.3 的一项新功能，该功能引入了相对时间节 first day of.本节可以与下个月、第五个月或+8个月结合使用以转到指定月份的第一天.您可以使用此代码获取下个月的第一天，而不是 +1 个月，如下所示:

modify('下个月的第一天');echo $d->format( 'F' ), "
";?>

此脚本将正确输出February.当 PHP 处理这个下个月的第一天节时，会发生以下事情:

1. next month 将月份数(原为 1)加 1.这使得日期为 2010-02-31.

2. first day of 将天数设置为 1，从而得到日期 2010-02-01.

I've been working a lot with the DateTime class and recently ran into what I thought was a bug when adding months. After a bit of research, it appears that it wasn't a bug, but instead working as intended. According to the documentation found here:

Example #2 Beware when adding or subtracting months

<?php
$date = new DateTime('2000-12-31');

$date->modify('+1 month');
echo $date->format('Y-m-d') . "
";

$date->modify('+1 month');
echo $date->format('Y-m-d') . "
";
?>

The above example will output:
2001-01-31
2001-03-03

Can anyone justify why this isn't considered a bug?

Furthermore does anyone have any elegant solutions to correct the issue and make it so +1 month will work as expected instead of as intended?

解决方案

Why it's not a bug:

The current behavior is correct. The following happens internally:

1. +1 month increases the month number (originally 1) by one. This makes the date 2010-02-31.

2. The second month (February) only has 28 days in 2010, so PHP auto-corrects this by just continuing to count days from February 1st. You then end up at March 3rd.

How to get what you want:

To get what you want is by: manually checking the next month. Then add the number of days next month has.

I hope you can yourself code this. I am just giving what-to-do.

PHP 5.3 way:

To obtain the correct behavior, you can use one of the PHP 5.3's new functionality that introduces the relative time stanza first day of. This stanza can be used in combination with next month, fifth month or +8 months to go to the first day of the specified month. Instead of +1 month from what you're doing, you can use this code to get the first day of next month like this:

<?php
$d = new DateTime( '2010-01-31' );
$d->modify( 'first day of next month' );
echo $d->format( 'F' ), "
";
?>

This script will correctly output February. The following things happen when PHP processes this first day of next month stanza:

1. next month increases the month number (originally 1) by one. This makes the date 2010-02-31.

2. first day of sets the day number to 1, resulting in the date 2010-02-01.

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