Description:
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There need to be an easy way to create DateTime object from unix timestamp when "declare(strict_types=1)" is set. The problem is "createFromFormat" expects second parameter to be a string and it forces it to be casted into string.

There are other ways also but not quite simple (see the attached code).

It would be simple and easy if there is a factory method:
DateTime::createFromTimestamp(int $timestamp)

This was requested before the release of "strict_types", original feature request: https://bugs.php.net/bug.php?id=43595

Test script:
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<?php
declare(strict_types=1);

//    get timestmap as int from model
//    for test lets set the current time.
$timestamp  = time();

//  Option: 1
$dateTime   = DateTime::createFromFormat('U', (string)$timestamp);

//  Option: 2a
$dateTime   = new DateTime();
$dateTime->setTimestamp($timestamp);

//  Option: 2b
$dateTime   = (new DateTime())->setTimestamp($timestamp);

//  While it could have been simpler:
//  $dateTime   = DateTime::createFromTimestamp($timestamp);