DateTime::sub

date_sub

(PHP 5 >= 5.3.0)

DateTime::sub -- date_sub Subtracts an amount of days, months, years, hours, minutes and seconds from a DateTime object

Description

Object oriented style

public DateTime DateTime::sub ( DateInterval $interval )

Procedural style

DateTime date_sub ( DateTime $object , DateInterval $interval )

Subtracts the specified DateInterval object from the specified DateTime object.

Parameters

object

Procedural style only: A DateTime object returned by date_create(). The function modifies this object.

interval

A DateInterval object

Return Values

Returns the DateTime object for method chaining or FALSE on failure.

Examples

Example #1 DateTime::sub() example

Object oriented style

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

Procedural style

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

The above examples will output:

2000-01-10

Example #2 Further DateTime::sub() examples

<?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";
?>

The above example will output:

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

Example #3 Beware when subtracting months

<?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";
?>

The above example will output:

2001-03-30
2001-03-02

Notes

DateTime::modify() is an alternative when using PHP 5.2.

See Also

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User Contributed Notes 3 notes

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4
Anonymous
3 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.)
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1
itonohito
14 days 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
3 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.
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