This small library adds a polyfill for the DateTimeImmutable object introduced in PHP 5.5.0.

• Chris Wilkinson

It's partially based on Benjamin Eberlei's Immutable DateTime Objects blog post.

$ php composer.phar require thewilkybarkid/date-time-immutable:~1.0

$dateTime = new DateTimeImmutable();
$newDateTime = $datetime->modify('+1 day');
var_dump($dateTime === $newDateTime); // output 'bool(false)'

PHP 5.5.0 also introduced a DateTimeInterface which both DateTimeImmutable and DateTime implement. In this polyfill we can't change the DateTime class, so DateTimeImmutable has to extend it. This is slightly dangerous as their behaviour is not compatible (see https://bugs.php.net/bug.php?id=64513).

PHP 5.6.0 added a DateTimeImmutable::createFromMutable() factory method, which this polyfill doesn't include.