setISODate to set ISO date in PHP

date_isodate_set ($date_obj,$year, $week,$day);

Parameter	DESCRIPTION
$date_obj	Required : Input date object to be assigned new value.
$year	Required: Year in 4 digit.
$week	Required: week of the year , starting from 1st week as 1
$day	Optional: default value is 1 , offset from 1st day of the week

Output is dateTime object, FALSE on failure.

Object Oriented style

First day of 2nd week of the year 2019.

$date = new DateTime();
$date->setISODate(2019, 2);
echo $date->format('Y-m-d'); // Output is 2019-01-07

3rd day of 5th week of year 2019

$date = new DateTime();
$date->setISODate(2019, 5,3);
echo $date->format('Y-m-d'); // Output is 2019-01-30

10th day of 4th week of year 2019

$date = new DateTime();
$date->setISODate(2019, 4,11);
echo $date->format('Y-m-d'); // Output is 2019-01-31

$date = date_create();
date_isodate_set($date, 2019, 25);
echo date_format($date, 'Y-m-d');  // Output is 2019-06-17

With $day value ( Optional )

$date = date_create();
date_isodate_set($date, 2019, 25,5);
echo date_format($date, 'Y-m-d');  // Output is 2019-06-21