PHP date_isodate_set() Function

Set the ISO date to the 5th week in 2013:

<?php
$date=date_create();
date_isodate_set($date,2013,5);
echo date_format($date,"Y-m-d");
?>

Definition and Usage

The date_isodate_set() function sets a date according to the ISO 8601 standard, using weeks and day offsets (instead of using a specific date).

date_isodate_set( object, year, week, day)

Parameter	Description
object	Required. Specifies a DateTime object returned by date_create()
year	Required. Specifies the year of the date
week	Required. Specifies the week of the date
day	Optional. Specifies the offset from the first day of the week. Default is 1

Return Value:	Returns a DateTime object on success. FALSE on failure
PHP Version:	5.2+
PHP Changelog:	PHP 5.3: Changed the return value from NULL to DateTime