PHP Manual: Sets the ISO date

Object-oriented style

public DateTime DateTime::setISODate(int $year, int $week, int $dayOfWeek = 1)

Procedural style

DateTime date_isodate_set(
    DateTime $object,
    int $year,
    int $week,
    int $dayOfWeek = 1
)

Set a date according to the ISO 8601 standard - using weeks and day offsets rather than specific dates.

Like DateTimeImmutable::setISODate but works with DateTime.

The procedural version takes the DateTime object as its first argument.

object: Procedural style only: A DateTime object returned by date_create. The function modifies this object.
year: Year of the date.
week: Week of the date.
dayOfWeek: Offset from the first day of the week.

Returns the modified DateTime object for method chaining.

DateTime::setISODate