DateInterval::__construct

Creates a new DateInterval object

&reftitle.description; public `DateInterval::__construct` `string` `interval_spec`

Creates a new DateInterval object.

&reftitle.parameters;

`interval_spec`

- 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`.

  ## `interval_spec` Period Designators

  Period Designator | Description
  `Y` | years
  `M` | months
  `D` | days
  `W` | weeks. These get converted into days, so 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`.

  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.

&reftitle.errors;

Throws an `Exception` when the `interval_spec` cannot be parsed as an interval.

&reftitle.examples;

### `DateInterval` example

    <?php

    $interval = new DateInterval('P2Y4DT6H8M');
    var_dump($interval);

    ?>

&example.outputs;

    object(DateInterval)#1 (8) {
      ["y"]=>
      int(2)
      ["m"]=>
      int(0)
      ["d"]=>
      int(4)
      ["h"]=>
      int(6)
      ["i"]=>
      int(8)
      ["s"]=>
      int(0)
      ["invert"]=>
      int(0)
      ["days"]=>
      bool(false)
    }

&reftitle.seealso;

- `DateInterval::format`
- `DateTime::add`
- `DateTime::sub`
- `DateTime::diff`