DateTime::setTimezone
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.)
DateTime::sub
date_sub
(PHP 5 >= 5.3.0)
DateTime::sub -- date_sub — 年月日時分秒の値を DateTime オブジェクトから引く
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
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
$date = date_create('2000-01-20');
date_sub($date, date_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
- DateTime::add() - 年月日時分秒の値を DateTime オブジェクトに加える
- DateTime::diff() - ふたつの DateTime オブジェクトの差を返す
- DateTime::modify() - タイムスタンプを変更する
add a note
User Contributed Notes
DateTime::sub
Anonymous
01-Feb-2011 07:15
php at keith tyler dot com
30-Nov-2010 11:53
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.