====== PHP RFC: DateTimeInterface removal ======
  * Version: 0.1
  * Date: 2015-07-21
  * Author: Marco Pivetta, ocramius@gmail.com
  * Status: Draft
  * First Published at: http://wiki.php.net/rfc/drop-datetimeinterface

The \DateTimeInterface is an implementation detail of ext/date that should not have been exposed to userland code.
The reason for it to be an internal detail is that ext/date does NOT rely on the interface itself, but on internal state of the \DateTime and \DateTimeImmutable implementations, as explained in [[https://github.com/php/php-src/pull/512|Pull request #512]] and [[https://bugs.php.net/bug.php?id=65768|Bug #65768]].

Because of the internal ext/date interactions, PHP 5.5.8 introduced a major BC break by making it [[http://3v4l.org/8GvgO|impossible to implement \DateTimeInterface in userland]].

This sort of behavior is what may become yet another of those quirks in the language that depreciate PHP.

===== Proposal =====

This RFC proposes its removal from PHP 7.0.0 even though it represents a BC break.

===== Alternatives =====

An alternative solution to the currently standing issue is to make ext/date rely on the interface internally, and therefore actually fix [[https://bugs.php.net/bug.php?id=65768|Bug #65768]].
There may not be enough time to do that, though, which is why this proposal is being advanced, rather than a more "elaborate" fix.

===== Backward Incompatible Changes =====

Applications relying on \DateTimeInterface would need to explicitly switch back to checking against \DateTime and \DateTimeImmutable.

Software compatible with PHP 5.5.0~5.5.7 and implementing \DateTimeInterface would break anyway.
Software checking against \DateTimeInterface via instanceof.

===== Proposed PHP Version(s) =====

PHP 7.0.0
List the proposed PHP versions that the feature will be included in.  Use relative versions such as "next PHP 5.x" or "next PHP 5.x.y".

===== RFC Impact =====

==== To Existing Extensions ====
ext/session

===== Proposed Voting Choices =====

2/3 majority due to major BC break involvement.

===== Patches and Tests =====
Links to any external patches and tests go here.

If there is no patch, make it clear who will create a patch, or whether a volunteer to help with implementation is needed.

Make it clear if the patch is intended to be the final patch, or is just a prototype.

===== Implementation =====

None, so far. Joe Watkins told me that he has a patch for it.