php.net |  support |  documentation |  report a bug |  advanced search |  search howto |  statistics |  random bug |  login

go to bug id or search bugs for

Bug #73348 A class can override a constant inherited from an indirect parent interface.
Submitted: 2016-10-19 13:08 UTC Modified: 2021-11-18 22:28 UTC
Votes:6
Avg. Score:3.7 ± 0.9
Reproduced:5 of 5 (100.0%)
Same Version:1 (20.0%)
Same OS:2 (40.0%)
From: mkh117 at gmail dot com Assigned: cmb (profile)
Status: Not a bug Package: Class/Object related
PHP Version: 7.0.12 OS: Ubuntu 16.04.1
Private report: No CVE-ID: None
View Developer Edit
Welcome back! If you're the original bug submitter, here's where you can edit the bug or add additional notes.
If you forgot your password, you can retrieve your password here.
Password:
Status:
Package:
Bug Type:
Summary:
From: mkh117 at gmail dot com
New email:
PHP Version: OS:

 

 [2016-10-19 13:08 UTC] mkh117 at gmail dot com 
Description:
------------
When a class inherits a constant from an interface that is not a direct parent of the class, it can override its value without any errors thrown.

Test script:
---------------
<?php
interface a {
  const con = 'Original value';	
}

abstract class b implements a {

}

class d extends b {
  const con='Overridden value';
}

echo d::con;

Expected result:
----------------
Fatal error:  Cannot inherit previously-inherited constant con from interface a ... on line 11

Actual result:
--------------
The script works and the interface constant is overridden.

Patches

Pull Requests

History

AllCommentsChangesGit/SVN commitsRelated reports
 [2016-10-19 15:17 UTC] cmb@php.net
-Status: Open +Status: Verified
 [2016-10-19 15:17 UTC] cmb@php.net 
Confirmed: <https://3v4l.org/u4Y1q>.
 [2016-10-21 15:42 UTC] leigh@php.net 
Related:

interface A {}
abstract class B implements A {}
class C extends B implements A {}

I would expect this to generate: "Class %s cannot implement previously implemented interface %s"

Both this and the constant override issue are handled by zend_do_implement_interface which is not called for for grandchildren implementors
 [2016-10-21 15:57 UTC] leigh@php.net 
Actually that might not be a bug, possibly designed to prevent:

class B implements A, A {}
 [2021-09-23 15:00 UTC] dktapps at pmmp dot io 
Is there any discussion on what to do about this problem? I just learned that a project of mine (with an API stable for 3 years) unintentionally exploited this bug, so I'd love to get an idea of whether I need to break BC to avoid my house burning down on a patch release.
 [2021-11-18 22:28 UTC] cmb@php.net
-Status: Verified +Status: Not a bug -Assigned To: +Assigned To: cmb
 [2021-11-18 22:28 UTC] cmb@php.net 
Actually, this is not a bug, but rather the fact that constants
defined in interfaces could not be overridden was.  This is all
resolved as of PHP 8.1.0[1] due to the introduction of final
constants[2].

> […], so I'd love to get an idea of whether I need to break BC to
> avoid my house burning down on a patch release.

No worries. :)

[1] <https://3v4l.org/c5dmY>
[2] <https://wiki.php.net/rfc/final_class_const>
 
PHP Copyright © 2001-2024 The PHP Group
All rights reserved. 		Last updated: Sat Nov 23 12:01:29 2024 UTC