PHP Manual: Returns new DateTimeImmutable instance encapsulating the given DateTime object

public static static DateTimeImmutable::createFromMutable(DateTime $object)

object: The mutable DateTime object that you want to convert to an immutable version. This object is not modified, but instead a new DateTimeImmutable instance is created containing the same date time and timezone information.

Returns a new DateTimeImmutable instance.

Version	Description
8.0.0	The method returns an instance of the currently invoked class now. Previously, it created a new instance of DateTimeImmutable.

Example #1 Creating an immutable date time object

<?php
$date = new DateTime("2014-06-20 11:45 Europe/London");

$immutable = DateTimeImmutable::createFromMutable( $date );
?>