DateTime::add

date_add

(PHP 5 >= 5.3.0, PHP 7)

DateTime::add -- date_add — Adds an amount of days, months, years, hours, minutes and seconds to a DateTime object

说明

面向对象风格

public DateTime DateTime::add ( DateInterval $interval )

过程化风格

DateTime date_add ( DateTime $object , DateInterval $interval )

Adds the specified DateInterval object to the specified DateTime object.

参数

object

仅过程化风格：由 date_create() 返回的 DateTime 类型的对象。此函数会修改这个对象。

interval

A DateInterval object

返回值

返回被修改的 DateTime 对象， 或者在失败时返回 FALSE.

范例

Example #1 DateTime::add() example

面向对象风格

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

过程化风格

<?php
$date = date_create('2000-01-01');
date_add($date, date_interval_create_from_date_string('10 days'));
echo date_format($date, 'Y-m-d');
?>

以上例程会输出：

2000-01-11

Example #2 Further DateTime::add() examples

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

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

以上例程会输出：

2000-01-01 10:00:30
2007-06-05 04:03:02

Example #3 Beware when adding months

<?php
$date = new DateTime('2000-12-31');
$interval = new DateInterval('P1M');

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

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

以上例程会输出：

2001-01-31
2001-03-03

注释

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

参见

User Contributed Notes

rnealxp at yahoo dot com 20-May-2017 12:43
What you can do with this function/method is a great example of the philosophy: "just because you can do it doesn't mean you should". I'm talking about two issues: (1) the number of days in the month which varies from months 1-12 as well as for month 2 which could be leap year (or not); and then issue (2): what if there is the need to specify a large quantity of an interval such that it needs to be re-characterized into broader-scoped intervals (i.e. 184 seconds ==> 3 minutes-4 seconds). Examples in notes elsewhere in the docs for this function illustrate both issues and their undesired effects so I won't focus on them further. But how did I decide to handle? I've gone with four "public" functions and a single "private" function, and without giving you a bunch of code to study, here are their summaries...

1. function adjustYear(int $yearsAdj){ //you can pass in +/- value and I adjust year value by that value but then I also call PHP's 'cal_days_in_month' function to ensure the day number I have in my date does not exceed days in the month for the new year/month combo--if it does, I adjust the day value downward.

2. function adjustMonth(int $monthsAdj){ //same notes as above apply; but also, I allow any number to be passed in for $monthsAdj. I use the 'int' function (int($monthsAdj/12)) and modulus % operator to determine how to adjust both year and month. And again, I use 'cal_days_in_month' function to tweak the day number as needed.

3. function addTime(int $days, int $hours, int $minutes, int $seconds){
// I use date_add and create a DateInterval object from the corresponding string spec (created from the args passed to this function). Note that months and years are excluded due to the bad side-effects already mentioned elsewhere.

4. function subtractTime(int $days, int $hours, int $minutes, int $seconds){
//notes for "addTime" also apply to this function but note that I like separate add and subtract functions because setting the DateInterval property flag to indicate add/subtract is not as intuitive for future coding.

5. function recharacterizeIntervals(int $days, int $hours, int $minutes, int $seconds){ // I convert excessively large quantities of any one interval into the next largest interval using the 'int' function and modulus (%) operator. I then use the result of this function when creating the string interval specification that gets passed when generating the DateInterval object for calling the date_add function (or object-method equivalent).

**Results/goals...
--any number of days/hours/minutes/seconds can be passed in to add/subtractTime and all of "Y/M/D/H/M/S" values get adjusted as you would expect.
--using adjustYear/Month lets you pass +/- values and only "Y/M" values get modified without having undesirable effects on day values.
--a call to the "recharacterize" function helps ensure proper and desired values are in the intervals prior to calling date_add to let it do its work.
dm at resource-ps dot co dot uk 11-Dec-2015 01:22
Be careful when using this function, I may have happened upon a bug in PHP7.

My code is as follows

//get date from post or else fill with today's date
if (isset($_POST["from"]))
{
$from = date_create($_POST["from"]);
}else{
$from = date_create(date("Y-m-d"));
}

//get date from post if there isn't one just take the same date as what is in the $from variable and add one day to it
if (isset($_POST["to"]))
{
$to = date_create($_POST["to"]);
}else{
    $to = $from;
date_modify($to, '+1 day');
}
echo(date_format($from, 'Y-m-d') . " " . date_format($to, 'Y-m-d'));

The resultant output is
$from = 2015-12-11
$to = 2015-12-11

In actuality the result should be
$from = 2015-12-10
$to = 2015-12-11

For some reason the code above modifies the $from variable in the line date_modify($to, '+1 day'); even though it shouldn't as the $from variable isn't being modified.

to fix this i needed to change the code to

//get date from post or else fill with today's date
if (isset($_POST["from"]))
{
$from = date_create($_POST["from"]);
}else{
$from = date_create(date("Y-m-d"));
}

//get date from post if there isn't one just take the same date as what is in the $from variable and add one day to it
if (isset($_POST["to"]))
{
$to = date_create($_POST["to"]);
}else{
    $to = date_create(date("Y-m-d"));
date_modify($to, '+1 day');
}
echo(date_format($from, 'Y-m-d') . " " . date_format($to, 'Y-m-d'));

This isn't strictly the code I wanted. Possible bug?
Angelo 19-Nov-2015 09:28
Another simple solution to adding a month but not autocorrecting days to the next month is this.
(Also works for substracting months)

$dt = new DateTime("2016-01-31");

$oldDay = $dt->format("d");
$dt->add(new DateInterval("P1M")); // 2016-03-02
$newDay = $dt->format("d");

if($oldDay != $newDay) {
    // Check if the day is changed, if so we skipped to the next month.
    // Substract days to go back to the last day of previous month.
    $dt->sub(new DateInterval("P" . $newDay . "D"));
}

echo $dt->format("Y-m-d"); // 2016-02-29

Hope this helps someone.
Anthony 01-Jul-2015 07:55
If you're using PHP >= 5.5, instead of using "glavic at gmail dot com"'s DateTimeEnhanced class, use the built in DateTimeImmutable type. When you call DateTimeImmutable::add() it will return a new object, rather than modifying the original
patrick dot mckay7 at gmail dot com 26-Nov-2014 01:34
Here is a solution to adding months when you want 2014-10-31 to become 2014-11-30 instead of 2014-12-01.

<?php

/**
 * Class MyDateTime
 *
 * Extends DateTime to include a sensible addMonth method.
 *
 * This class provides a method that will increment the month, and
 * if the day is greater than the last day in the new month, it
 * changes the day to the last day of that month. For example,
 * If you add one month to 2014-10-31 using DateTime::add, the
 * result is 2014-12-01. Using MyDateTime::addMonth the result is
 * 2014-11-30.
 */
class MyDateTime extends DateTime
{

    public function addMonth($num = 1)
    {
        $date = $this->format('Y-n-j');
        list($y, $m, $d) = explode('-', $date);

        $m += $num;
        while ($m > 12)
        {
            $m -= 12;
            $y++;
        }

        $last_day = date('t', strtotime("$y-$m-1"));
        if ($d > $last_day)
        {
            $d = $last_day;
        }

        $this->setDate($y, $m, $d);
    }

}

?>
artaxerxes2 at iname dot com 19-Sep-2013 04:28
Be careful that the internal timer to your DateTime object can be changed drastically when adding even 1 second, during the switch from DST to normal.
Consider the following:
<?php

$ts = 1383458399; /* 2013-11-03 01:59:59 in Eastern Saving Time */
$dst = DateTime::createFromFormat('U',$ts, new DateTimeZone('GMT')); /* timezone is ignored for a unix timestamp, but if we don't put it, php throws warnings */
$dst->setTimeZone(new DateTimeZone('EST5EDT')); /* a timezone effectuating the change */
$second = new DateInterval('PT1S'); /* one second */

echo $ts . "\t" . $dst->format("U\tY-m-d H:i:s T") . "\n";

$dst->add($second);
$ts++;

echo $ts . "\t" . $dst->format("U\tY-m-d H:i:s T") . "\n";

/* results:
1383458399    1383458399    2013-11-03 01:59:59 EDT
1383458400    1383462000    2013-11-03 02:00:00 EST

noticed how the second column went from 1383458399 to 1383462000 even though only 1 second was added?
*/

?>
glavic at gmail dot com 12-Sep-2013 10:06
If you need add() and sub() that don't modify object values, you can create new methods like this:

<?php

class DateTimeEnhanced extends DateTime {

    public function returnAdd(DateInterval $interval)
    {
        $dt = clone $this;
        $dt->add($interval);
        return $dt;
    }
   
    public function returnSub(DateInterval $interval)
    {
        $dt = clone $this;
        $dt->sub($interval);
        return $dt;
    }

}

$interval = DateInterval::createfromdatestring('+1 day');

$dt = new DateTimeEnhanced; # initialize new object
echo $dt->format(DateTime::W3C) . "\n"; # 2013-09-12T15:01:44+02:00

$dt->add($interval); # this modifies the object values
echo $dt->format(DateTime::W3C) . "\n"; # 2013-09-13T15:01:44+02:00

$dtNew = $dt->returnAdd($interval); # this returns the new modified object and doesn't change original object
echo $dt->format(DateTime::W3C) . "\n"; # 2013-09-13T15:01:44+02:00
echo $dtNew->format(DateTime::W3C) . "\n"; # 2013-09-14T15:01:44+02:00
Anonymous 01-Feb-2011 11:16
Note that the add() and sub() 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.)
fortruth at mabang dot net 24-Aug-2010 08:00
adding 15 min to a datetime

<?php
$initDate = new DateTime("2010/08/24");

$initDate->add(new DateInterval("PT15M"));
echo $initDate->format("Y/m/d m:i:s");//result: 2010/08/24 08:15:00
?>

period:
P1Y2M3DT1H2M3S

period time:
PT1H2M3S