ScotlandPHP

DateTime::sub

date_sub

(PHP 5 >= 5.3.0, PHP 7)

DateTime::sub -- date_sub 年月日時分秒の値を DateTime オブジェクトから引く

説明

オブジェクト指向型

public DateTime DateTime::sub ( DateInterval $interval )

手続き型

DateTime date_sub ( DateTime $object , DateInterval $interval )

指定した DateInterval オブジェクトを、 指定した DateTime オブジェクトから引きます。

パラメータ

object

手続き型のみ: date_create() が返す DateTime オブジェクト。 この関数は、このオブジェクトを変更します。

interval

DateInterval オブジェクト。

返り値

メソッドチェインに使う DateTime オブジェクトを返します。失敗した場合に FALSE を返します。

例1 DateTime::sub() の例

オブジェクト指向型

<?php
$date 
= new DateTime('2000-01-20');
$date->sub(new DateInterval('P10D'));
echo 
$date->format('Y-m-d') . "\n";
?>

手続き型

<?php
$date 
date_create('2000-01-20');
date_sub($datedate_interval_create_from_date_string('10 days'));
echo 
date_format($date'Y-m-d');
?>

上の例の出力は以下となります。

2000-01-10

例2 DateTime::sub() の別の例

<?php
$date 
= new DateTime('2000-01-20');
$date->sub(new DateInterval('PT10H30S'));
echo 
$date->format('Y-m-d H:i:s') . "\n";

$date = new DateTime('2000-01-20');
$date->sub(new DateInterval('P7Y5M4DT4H3M2S'));
echo 
$date->format('Y-m-d H:i:s') . "\n";
?>

上の例の出力は以下となります。

2000-01-19 13:59:30
1992-08-15 19:56:58

例3 月を減算するときの注意点

<?php
$date 
= new DateTime('2001-04-30');
$interval = new DateInterval('P1M');

$date->sub($interval);
echo 
$date->format('Y-m-d') . "\n";

$date->sub($interval);
echo 
$date->format('Y-m-d') . "\n";
?>

上の例の出力は以下となります。

2001-03-30
2001-03-02

注意

PHP 5.2 では、かわりに DateTime::modify() を使うことができます。

参考

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User Contributed Notes 5 notes

up
55
Anonymous
6 years ago
Note that the sub() and add() methods will modify the value of the object you're calling the method on! This is very untypical for a method that returns a value of its own type. You could misunderstand it that the method would return a new instance with the modified value, but in fact it modifies itself! This is undocumented here. (Only a side note on procedural style mentions it, but it obviously does not apply to object oriented style.)
up
-1
Anonymous
16 days ago
yeoo

is this in utc or not i have no clue
up
0
itonohito
3 years ago
When trying to pass daylight saving state change time, sub() works incorrectly.

$t = new DateTime( '2014-03-30 02:00:00' );
$t->add( new DateInterval('PT1H') );
echo $->format('Y-m-d H:i:s');

output will be: '2014-03-30 04:00:00'.

Well, it's ok because at 3:00 a.m. daylight saving time begins in my country, so after  02:59:59 must be 04:00:00.

But if I try to subtract time:

$t = new DateTime( '2014-03-30 04:00:00' );
$t->sub( new DateInterval('PT1H') );
echo $->format('Y-m-d H:i:s');

output will be: '2014-03-30 04:00:00'.

Yes, completely the same, not '2014-03-30 02:00:00' as it should be.
up
0
php at keith tyler dot com
6 years ago
If you use diff() after sub(), the effects of the sub() will be repeated on the date object.

It doesn't matter if the object is the one diffed or doing the diffing (i.e. which object you call diff() from).

<?php
$today
= new DateTime();
$newdate = new DateTime();

print_r($newdate);
$newdate->sub(new DateInterval("PT1S"));
print_r($newdate);
$s = $newdate->diff($today);
print_r($newdate);
$s = $today->diff($newdate);
print_r($newdate);
$s = $today->diff($newdate);
print_r($newdate);
?>

Prints:

DateTime Object
(
    [date] => 2010-11-30 18:43:48
    [timezone_type] => 3
    [timezone] => America/Los_Angeles
)
DateTime Object
(
    [date] => 2010-11-30 18:43:47
    [timezone_type] => 3
    [timezone] => America/Los_Angeles
)
DateTime Object
(
    [date] => 2010-11-30 18:43:46
    [timezone_type] => 3
    [timezone] => America/Los_Angeles
)
DateTime Object
(
    [date] => 2010-11-30 18:43:45
    [timezone_type] => 3
    [timezone] => America/Los_Angeles
)
DateTime Object
(
    [date] => 2010-11-30 18:43:44
    [timezone_type] => 3
    [timezone] => America/Los_Angeles
)

Note that using add() instead of sub() does NOT have the same effect.

This is particularly undesirable -- in this example you make a datetime, use sub() to make it a relative time in the past, and then date->diff() to confirm the difference. But the diff() inadvertendly makes the difference 2x.
up
-6
soerenklein98 at gmail dot com
2 years ago
Keep in mind that this method can work incorrectly when the daylight saving time is changing to wintertime.
An example is when you have got a loop and your subtracting 1 hour from your time in it. On one day you are actually subtracting 1 hour and the computer adds 1 - the infinitive loop is created.
And on the other day you would actually subtract 2 hours.
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