PHP Manual: DateTimeImmutable::modify

Description

#[\NoDiscard(message: "as DateTimeImmutable::modify() does not modify the object itself")]
public function DateTimeImmutable::modify(string $modifier): DateTimeImmutable

Creates a new DateTimeImmutable object with modified timestamp. The original object is not modified.

Parameters

modifier: A date/time string. Valid formats are explained in Date and Time Formats.

Return Values

Returns DateTimeImmutable on success. Procedural style returns false on failure.

Errors/Exceptions

If an invalid Date/Time string is passed, DateMalformedStringException is thrown. Previous to PHP 8.3, this was a warning.

Changelog

Version	Description
8.4.0	Now has a tentative return type of DateTimeImmutable. Previously it was DateTimeImmutable\|false.
8.3.0	DateTimeImmutable::modify() now throws DateMalformedStringException if an invalid string is passed. Previously, it returned `false`, and a warning was emitted.

Examples

Example #1 DateTimeImmutable::modify() example

Object-oriented style

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

The above example will output:

2006-12-13

Example #2 Beware when adding or subtracting months

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

$newDate1 = $date->modify('+1 month');
echo $newDate1->format('Y-m-d') . "\n";

$newDate2 = $newDate1->modify('+1 month');
echo $newDate2->format('Y-m-d') . "\n";