DateInterval::__construct

    (PHP 5 >= 5.3.0, PHP 7, PHP 8)

    DateInterval::__construct — Creates a new DateInterval object

    Description

    public DateInterval::__construct(string $duration)

    Creates a new DateInterval object.

    Parameters

    duration

    An interval specification.

    The format starts with the letter P, for period. Each duration period is represented by an integer value followed by a period designator. If the duration contains time elements, that portion of the specification is preceded by the letter T.

    duration Period Designators
    Period Designator Description
    Y years
    M months
    D days
    W weeks. Converted into days. Prior to PHP 8.0.0, can not be combined with D.
    H hours
    M minutes
    S seconds

    Here are some simple examples. Two days is P2D. Two seconds is PT2S. Six years and five minutes is P6YT5M.

    Note:

    The unit types must be entered from the largest scale unit on the left to the smallest scale unit on the right. So years before months, months before days, days before minutes, etc. Thus one year and four days must be represented as P1Y4D, not P4D1Y.

    The specification can also be represented as a date time. A sample of one year and four days would be P0001-00-04T00:00:00. But the values in this format can not exceed a given period's roll-over-point (e.g. 25 hours is invalid).

    These formats are based on the » ISO 8601 duration specification.

    Errors/Exceptions

    Throws an DateMalformedIntervalStringException when the duration cannot be parsed as an interval. Prior to PHP 8.3, this was Exception.

    Changelog

    Version Description
    8.3.0 Now throws DateMalformedIntervalStringException instead of Exception.
    8.2.0 Only the y to f, invert, and days will be visible, including a new from_string boolean property.
    8.0.0 W can be combined with D.

    Examples

    Example #1 Constructing and using DateInterval objects

    <?php
    // Create a specific date
    $someDate = \DateTime::createFromFormat("Y-m-d H:i", "2022-08-25 14:18");

    // Create interval
    $interval = new \DateInterval("P7D");

    // Add interval
    $someDate->add($interval);

    // Convert interval to string
    echo $interval->format("%d");

    The above example will output:


    7

    Example #2 DateInterval example

    <?php

    $interval     = new DateInterval('P1W2D');
    var_dump($interval);

    ?>

    Output of the above example in PHP 8.2:

    object(DateInterval)#1 (10) {
  ["y"]=>
  int(0)
  ["m"]=>
  int(0)
  ["d"]=>
  int(9)
  ["h"]=>
  int(0)
  ["i"]=>
  int(0)
  ["s"]=>
  int(0)
  ["f"]=>
  float(0)
  ["invert"]=>
  int(0)
  ["days"]=>
  bool(false)
  ["from_string"]=>
  bool(false)
}

    Output of the above example in PHP 8:

    object(DateInterval)#1 (16) {
  ["y"]=>
  int(0)
  ["m"]=>
  int(0)
  ["d"]=>
  int(9)
  ["h"]=>
  int(0)
  ["i"]=>
  int(0)
  ["s"]=>
  int(0)
  ["f"]=>
  float(0)
  ["weekday"]=>
  int(0)
  ["weekday_behavior"]=>
  int(0)
  ["first_last_day_of"]=>
  int(0)
  ["invert"]=>
  int(0)
  ["days"]=>
  bool(false)
  ["special_type"]=>
  int(0)
  ["special_amount"]=>
  int(0)
  ["have_weekday_relative"]=>
  int(0)
  ["have_special_relative"]=>
  int(0)
}

    Output of the above example in PHP 7:

    object(DateInterval)#1 (16) {
  ["y"]=>
  int(0)
  ["m"]=>
  int(0)
  ["d"]=>
  int(2)
  ["h"]=>
  int(0)
  ["i"]=>
  int(0)
  ["s"]=>
  int(0)
  ["f"]=>
  float(0)
  ["weekday"]=>
  int(0)
  ["weekday_behavior"]=>
  int(0)
  ["first_last_day_of"]=>
  int(0)
  ["invert"]=>
  int(0)
  ["days"]=>
  bool(false)
  ["special_type"]=>
  int(0)
  ["special_amount"]=>
  int(0)
  ["have_weekday_relative"]=>
  int(0)
  ["have_special_relative"]=>
  int(0)
}

    See Also

    • DateInterval::format() - Formats the interval
    • DateTime::add() - Modifies a DateTime object, with added amount of days, months, years, hours, minutes and seconds
    • DateTime::sub() - Subtracts an amount of days, months, years, hours, minutes and seconds from a DateTime object
    • DateTime::diff() - Returns the difference between two DateTime objects

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    User Contributed Notes 14 notes

    up
    109
    owen at beliefs.com
    11 years ago
    M is used to indicate both months and minutes.

    As noted on the referenced wikipedia page for ISO 6801 http://en.wikipedia.org/wiki/Iso8601#Durations

    To resolve ambiguity, "P1M" is a one-month duration and "PT1M" is a one-minute duration (note the time designator, T, that precedes the time value).

    Using: PHP 5.3.2-1ubuntu4.19

    // For 3 Months
    $dateTime = new DateTime;echo $dateTime->format( DateTime::ISO8601 ), PHP_EOL;
    $dateTime->add(new DateInterval("P3M"));
    echo $dateTime->format( DateTime::ISO8601 ), PHP_EOL;
    Results in:
    2013-07-11T11:12:26-0400
    2013-10-11T11:12:26-0400

    // For 3 Minutes
    $dateTime = new DateTime;echo $dateTime->format( DateTime::ISO8601 ), PHP_EOL;
    $dateTime->add(new DateInterval("PT3M"));
    echo $dateTime->format( DateTime::ISO8601 ), PHP_EOL;
    Results in:
    2013-07-11T11:12:42-0400
    2013-07-11T11:15:42-0400

    Insert a T after the P in the interval to add 3 minutes instead of 3 months.
    up
    11
    Hernanibus
    6 years ago
    It is not stated, but you cannot create directly a negative interval, this is you cannot create a "-2 days" interval as:

    <?
    $interval = new DateInterval("P-2D");//or
    $interval = new DateInterval("-P2D");
    ?>

    Instead you have to create first the interval and then set its 'invert' property to 1, this is:

    <?
    $interval = new DateInterval("P2D");
    $interval->invert = 1;
    ?>

    Then you should keep in mind that this interval acts as a negative number, hence to subtract the interval from a given date you must 'add' it:

    <?
    $interval = new DateInterval("P2D");
    $interval->invert = 1;
    $date = new DateTime ("1978-01-23 17:46:00");
    $date->add($interval)->format("Y-m-d H:i:s");//this is "1978-01-21 17:46:00"
    ?>
    up
    29
    kuzb
    13 years ago
    It should be noted that this class will not calculate days/hours/minutes/seconds etc given a value in a single denomination of time. For example:

    <?php
    $di     = new DateInterval('PT3600S');
    echo     $di->format('%H:%i:%s');

    ?>

    will yield 0:0:3600 instead of the expected 1:0:0
    up
    15
    admin at torntech dot com
    9 years ago
    Warning - despite the $interval_spec accepting the ISO 8601 specification format, it does not accept decimal fraction values with period or comma as stated in the specification.

    https://bugs.php.net/bug.php?id=53831

    <?php
    /* Example from ISO 8601 documentation */
    $interval = new DateInterval('P0.5Y');
    ?>

    Will result in
    Fatal error: Uncaught exception 'Exception' with message 'DateInterval::__construct(): Unknown or bad format (P0.5Y)'
    up
    20
    buvinghausen at gmail dot com
    12 years ago
    I think it is easiest if you would just use the sub method on the DateTime class.

    <?php
    $date     = new DateTime();
    $date->sub(new DateInterval("P89D"));
    up
    2
    Anonymous
    3 years ago
    Note that to add time you must enter P even though the period is empty.

    To add 1 hour :

    <?php

    $plusOneHour     = (new DateTime('now'))->add(new DateInterval("PT1H"));

    var_dump($plusOneHour);

    ?>
    up
    10
    kevinpeno at gmail dot com
    13 years ago
    Note that, while a DateInterval object has an $invert property, you cannot supply a negative directly to the constructor similar to specifying a negative in XSD ("-P1Y"). You will get an exception through if you do this.

    Instead you need to construct using a positive interval ("P1Y") and the specify the $invert property === 1.
    up
    10
    daniellehr at gmx dot de
    12 years ago
    Alternatively you can use DateInterval::createFromDateString() for negative intervals:

    <?php
    $date     = new DateTime();
    $date->add(DateInterval::createFromDateString('-89 days'));
    up
    11
    userexamplecom at mailinator dot com
    8 years ago
    Take care, if you have a DateTime Object on the 31h of January and add Da DateInterval of one Month, then you are in March instead of February.

    For Example:
    ---
    // given the actual date is 2017-01-31
    $today = new DateTime('now', $timeZoneObject);
    $today->add(new DateInterval('P1M'));
    echo $today->format('m');
    // output: 03
    ---
    up
    5
    jawzx01 at gmail dot com
    12 years ago
    As previously mentioned, to do a negative DateInterval object, you'd code:

    <?php
    $date1     = new DateTime();
    $eightynine_days_ago = new DateInterval( "P89D" );
    $eightynine_days_ago->invert = 1; //Make it negative.
    $date1->add( $eightynine_days_ago );
    ?>

    and then $date1 is now 89 days in the past.
    up
    1
    sloanlance+php.net gmail com
    6 years ago
    ⚠️ It's important to remember the warning about DateInterval given by "admin at torntech dot com" in an earlier comment (http://php.net/manual/en/dateinterval.construct.php#116750). To reiterate:

    Some versions of PHP (e.g., 5.6.31) have a bug that disallows fractional parts in a ISO 8601 duration string given as the argument for the DateInterval constructor. That is, these examples will fail:

    <?php
    // 'P0.5Y' is valid according to ISO 8601
    $interval = new DateInterval('P0.5Y'); // Throws exception
    ?>

    <?php
    // 'PT585.829S' is valid according to ISO 8601
    $interval = new DateInterval('PT585.829S'); // Throws exception
    ?>

    If this bug affects you, please go to the report for this bug in the PHP Bug Tracking System, and place a vote stating that it affects you: https://bugs.php.net/bug.php?id=53831
    up
    2
    lsloan-php dot net at umich dot edu
    8 years ago
    Although PHP refers to periods of time as "intervals", ISO 8601 refers to them as "durations". In ISO 8601, "intervals" are something else.

    While ISO 8601 allows fractions for all parts of a duration (e.g., "P0.5Y"), DateInterval does not. Use caution when calculating durations. If the duration has a fractional part, it may be lost when storing it in a DateInterval object.
    up
    0
    Ray.Paseur sometimes uses Gmail
    8 years ago
    To recover the interval specification string:

    <?php
    function get_interval_spec(DateTime $alpha, DateTime $omega)
    {
    $intvl = $alpha->diff($omega);

    $date = NULL;
    if (    $intvl->y) $date .= $intvl->y . 'Y';
    if (    $intvl->m) $date .= $intvl->m . 'M';
    if (    $intvl->d) $date .= $intvl->d . 'D';

    $time = NULL;
    if (    $intvl->h) $time .= $intvl->h . 'H';
    if (    $intvl->i) $time .= $intvl->i . 'M';
    if (    $intvl->s) $time .= $intvl->s . 'S';
    if (    $time) $time = 'T' . $time;

    $text ='P' . $date . $time;
    if (    $text == 'P') return 'PT0S';
    return     $text;
    }
    up
    -1
    grzeniufication
    4 years ago
    If you'd like to persist an interval object in a DB it could be handy to implement the __toString() method. A formatted interval value can be easier to read by a human than the output of serialize. Here's an example:

    <?php

    namespace App;

    class     DateInterval extends \DateInterval
    {
    public function     __toString()
    {
    return     $this->format('P%yY%mM%dDT%hH%iM%sS');
    }
    }

    $interval1 = new DateInterval('P1Y');
    $interval2 = new DateInterval(strval($interval1));
    assert($interval1 == $interval2);
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