Bug #63976 [NEW]: Parent class incorrectly using child constant in class property

From: Date: Sat, 12 Jan 2013 03:51:21 +0000
Subject: Bug #63976 [NEW]: Parent class incorrectly using child constant in class property
Groups: php.bugs 
Request: Send a blank email to php-bugs+get-175969@lists.php.net to get a copy of this message 
From:             don at smugmug dot com
Operating system: Ubuntu 12.04
PHP version:      5.4.10
Package:          Class/Object related
Bug Type:         Bug
Bug description:Parent class incorrectly using child constant in class property

Description:
------------
Class properties that rely on potentially inherited class constants have 
unpredictable behavior.

Since PHP doesn't support Child class properties referencing static values
like 
static::CONST, the meaning of self::CONST is ambiguous. One of two things
should 
happen:

1. It should use the value defined in the actual class in question (like
self:: 
is used throughout the rest of PHP).

2. It should treat self:: in this case, since it's compile-time and not
late 
static binding, like static:: and walk the inheritance tree, delivering the

result for the Child class.

Option #1 seems the most sane, but PHP often behaves like it intends #2 to
work. 
But not always...

In the provided examples, 'brokenA.php' behaves like #1, above, while 
'brokenB.php' and 'brokenC.php' behave like #2. The only thing that's
changed is 
the order in which the classes are require()'d.

In a complex script, with autoloaders, class instantiation order isn't 
predictable, of course, resulting in unpredictable results.

Test script:
---------------
Example code: https://github.com/onethumb/php-parent-child-constant-bug

Expected result:
----------------
Consistent results for Baz->table.  Either 'foo' or 'baz' 100% of the time,
rather 
than mixed up depending on require() order.

Have a preference for adding static::CONST to PHP and making self::CONST
behave 
like self:: does in the rest of the language (resulting in Baz->table ==
'baz' in 
the examples if we used static::CONST), but if that's not preferable for
some 
reason, self::CONST should probably behave like self:: everywhere else
(resulting 
in Baz->table == 'foo' in the examples).

Actual result:
--------------
brokenA.php:
Bar Object
(
    [table] => bar
)
Baz Object
(
    [table] => foo
)

brokenB.php:
Bar Object
(
    [table] => bar
)
Baz Object
(
    [table] => baz
)

brokenC.php:
Baz Object
(
    [table] => baz
)
Bar Object
(
    [table] => bar
)
Baz Object
(
    [table] => baz
)

-- 
Edit bug report at https://bugs.php.net/bug.php?id=63976&edit=1
-- 
Try a snapshot (PHP 5.4):   https://bugs.php.net/fix.php?id=63976&r=trysnapshot54
Try a snapshot (PHP 5.3):   https://bugs.php.net/fix.php?id=63976&r=trysnapshot53
Try a snapshot (trunk):     https://bugs.php.net/fix.php?id=63976&r=trysnapshottrunk
Fixed in SVN:               https://bugs.php.net/fix.php?id=63976&r=fixed
Fixed in release:           https://bugs.php.net/fix.php?id=63976&r=alreadyfixed
Need backtrace:             https://bugs.php.net/fix.php?id=63976&r=needtrace
Need Reproduce Script:      https://bugs.php.net/fix.php?id=63976&r=needscript
Try newer version:          https://bugs.php.net/fix.php?id=63976&r=oldversion
Not developer issue:        https://bugs.php.net/fix.php?id=63976&r=support
Expected behavior:          https://bugs.php.net/fix.php?id=63976&r=notwrong
Not enough info:            https://bugs.php.net/fix.php?id=63976&r=notenoughinfo
Submitted twice:            https://bugs.php.net/fix.php?id=63976&r=submittedtwice
register_globals:           https://bugs.php.net/fix.php?id=63976&r=globals
PHP 4 support discontinued: https://bugs.php.net/fix.php?id=63976&r=php4
Daylight Savings:           https://bugs.php.net/fix.php?id=63976&r=dst
IIS Stability:              https://bugs.php.net/fix.php?id=63976&r=isapi
Install GNU Sed:            https://bugs.php.net/fix.php?id=63976&r=gnused
Floating point limitations: https://bugs.php.net/fix.php?id=63976&r=float
No Zend Extensions:         https://bugs.php.net/fix.php?id=63976&r=nozend
MySQL Configuration Error:  https://bugs.php.net/fix.php?id=63976&r=mysqlcfg

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