DateTime::modify

date_modify

(PHP 5 >= 5.2.0, PHP 7, PHP 8)

DateTime::modify -- date_modify — Alters the timestamp

Description

Object-oriented style

public DateTime::modify(string $modifier): DateTime|false

Procedural style

date_modify(DateTime $object, string $modifier): DateTime|false

Alter the timestamp of a DateTime object by incrementing or decrementing in a format accepted by DateTimeImmutable::__construct().

Parameters

object: Procedural style only: A DateTime object returned by date_create(). The function modifies this object.
modifier: A date/time string. Valid formats are explained in Date and Time Formats.

Return Values

Returns the modified DateTime object for method chaining or false on failure.

Errors/Exceptions

Object Orientated API only: If an invalid Date/Time string is passed, DateMalformedStringException is thrown.

Changelog

Version	Description
8.3.0	Now throws DateMalformedStringException with DateTime::modify() if an invalid string is passed, instead of a warning. date_modify() has not been changed.

Examples

Example #1 DateTime::modify() example

Object-oriented style

<?php
$date = new DateTime('2006-12-12');
$date->modify('+1 day');
echo $date->format('Y-m-d');
?>

Procedural style

<?php
$date = date_create('2006-12-12');
date_modify($date, '+1 day');
echo date_format($date, 'Y-m-d');
?>

The above examples will output:

2006-12-13

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') . "\n";

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

The above example will output:

2001-01-31
2001-03-03

Example #3 All formats of Date and Time are supported

<?php
$date = new DateTime('2020-12-31');

$date->modify('July 1st, 2023');
echo $date->format('Y-m-d H:i') . "\n";

$date->modify('Monday next week');
echo $date->format('Y-m-d H:i') . "\n";

$date->modify('17:30');
echo $date->format('Y-m-d H:i') . "\n";
?>

The above example will output:

2023-07-01 00:00
2023-07-03 00:00
2023-07-03 17:30

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User Contributed Notes 1 note

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php_net at striderweb dot com ¶

4 months ago

You have to be a bit careful with variables here. If for example you want to add a variable amount of minutes you might use `->modify("+$min").  This will not work out if `$min` is a negative number, because modify will see the "+" and ignore the "-".  If `$min` equals -10, modify in this example will add ten minutes, not subtract!

What is happening is if the modify string has two operations, the first will be obeyed and later ones will be ignored.

So "+-10 minutes" will add ten minutes, even though you might expect it to add the negative number.  Similarly "--10 minutes" will subtract ten minutes, despite the apparent logic of subtracting a negative number.