DateTime::add()
date_add
(PHP 5 >= 5.3.0, PHP 7)
给一个 DateTime 对象增加一定量的天，月，年，小时，分钟以及秒。
说明
面向对象风格public DateTime::add(DateInterval$interval): DateTime
过程化风格
date_add(DateTime$object,DateInterval$interval): DateTime
将给定的DateInterval对象加到DateTime对象上。
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
DateInterval对象。
返回值
返回被修改的 DateTime 对象，或者在失败时返回FALSE.
范例
Example #1DateTime::add()例程
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
FurtherDateTime::add()例程
<?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
当在 DateTime 上加月的时候要注意
<?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
在 PHP 5.2 的版本中，也可以使用DateTime::modify()方法来替代本方法。
参见
- DateTime::sub() 对一个 DateTime 对象减去一定量的日、月、年、小时、分钟和秒。
- DateTime::diff() Returns the difference between two DateTime objects
- DateTime::modify() 修改日期时间对象的值
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.)
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 $dt->format("Y-m-d"); // 2016-02-29
Hope this helps someone.If you're using PHP >= 5.5, instead of using "glavic at gmail dot com"'s DateTimeEnhanced class, use the built in DateTimeImmutable type. When you call DateTimeImmutable::add() it will return a new object, rather than modifying the original
Here is a solution to adding months when you want 2014-10-31 to become 2014-11-30 instead of 2014-12-01.
<?php
/**
* Class MyDateTime
*
* Extends DateTime to include a sensible addMonth method.
*
* This class provides a method that will increment the month, and
* if the day is greater than the last day in the new month, it
* changes the day to the last day of that month. For example,
* If you add one month to 2014-10-31 using DateTime::add, the
* result is 2014-12-01. Using MyDateTime::addMonth the result is
* 2014-11-30.
*/
class MyDateTime extends DateTime
{
public function addMonth($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);
}
}
?>
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+02:00Be 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?
*/
?>
If you use fraction of seconds, you may have surprises. It only occurs when the sum of the floating point parts results in exactly 1 second (0.5 + 0.5 ou 0.3 + 0.7, for example). See these cases at intervals slightly bigger than 1 second:
<?php
$objDataHora = date_create("2017-12-31T23:59:59.300");
$objIntervalo = new DateInterval("PT0S");
$objIntervalo->f = 0.600;
$objDataHora = date_add($objDataHora, $objIntervalo);
$strDataHora = date_format($objDataHora, "Y-m-d\TH:i:s.v");
?>
$strDataHora is correct: "2017-12-31T23:59:59.900"
<?php
$objDataHora = date_create("2017-12-31T23:59:59.300");
$objIntervalo = new DateInterval("PT0S");
$objIntervalo->f = 0.800;
$objDataHora = date_add($objDataHora, $objIntervalo);
$strDataHora = date_format($objDataHora, "Y-m-d\TH:i:s.v");
?>
$strDataHora is correct: "2018-01-01T00:00:00.100"
But...
<?php
$objDataHora = date_create("2017-12-31T23:59:59.300");
$objIntervalo = new DateInterval("PT0S");
$objIntervalo->f = 0.700;
$objDataHora = date_add($objDataHora, $objIntervalo);
$strDataHora = date_format($objDataHora, "Y-m-d\TH:i:s.v");
?>
$strDataHora has "2017-12-31T23:59:59.1000"
To resolve, add 1 second to the interval and f property must be negative (-1.0 plus original value):
<?php
$objDataHora = date_create("2017-12-31T23:59:59.300");
$objIntervalo = new DateInterval("PT1S");
$objIntervalo->f = -0.300; // = -1.0 + 0.700
$objDataHora = date_add($objDataHora, $objIntervalo);
$strDataHora = date_format($objDataHora, "Y-m-d\TH:i:s.v");
?>
$strDataHora is correct: "2018-01-01T00:00:00.000"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 $seconds){ // I convert excessively large quantities of any one interval into the next largest interval using the 'int' function and modulus (%) operator. I then use the result of this function when creating the string interval specification that gets passed when generating the DateInterval object for calling the date_add function (or object-method equivalent).
**Results/goals...
--any number of days/hours/minutes/seconds can be passed in to add/subtractTime and all of "Y/M/D/H/M/S" values get adjusted as you would expect.
--using adjustYear/Month lets you pass +/- values and only "Y/M" values get modified without having undesirable effects on day values.
--a call to the "recharacterize" function helps ensure proper and desired values are in the intervals prior to calling date_add to let it do its work.Be careful when using this function, I may have happened upon a bug in PHP7.
My code is as follows
//get date from post or else fill with today's date
if (isset($_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?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