Bug #68485 [Nab]: late namespace resolution with cross-namespace inheritance missing
Edit report at https://bugs.php.net/bug.php?id=68485&edit=1
ID: 68485
Updated by: requinix@php.net
Reported by: llmll at gmx dot de
Summary: late namespace resolution with cross-namespace
inheritance missing
Status: Not a bug
Type: Bug
Package: Class/Object related
Operating System: any
PHP Version: 5.5.19
Block user comment: N
Private report: N
New Comment:
There is no inheritance in the first place. "Helper::$Value" does not work as a relative
path but is merely shorthand for writing "\Alpha\Helper::$Value", and was resolved as such
at compile-time.
The feature you're trying to report a bug for *does not exist*.
Previous Comments:
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[2014-11-23 23:59:53] llmll at gmx dot de
The example shows a clear breach in namespace/inheritance logic - this qualifies as bug.
As you explain a mere c&p of the method to the new class would resolve the issue. I remeber
reading nearly the same tips here, when LSB wasn't there and people claimed __CLASS__ was
sufficient for everything and for everything else just c&p. I personally stay away from hackish
tricks, the important namespace functionality should be consistent. So my suggestion is focusing on
the problem not the alternatives.
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[2014-11-23 23:43:11] requinix@php.net
That may be but it's still not a bug. There is no such feature like what you're
describing; the closest is LSB which is why I brought it up.
Your options include
a) Beta\Base redefining Write() to use the Helper class that it wants to use.
b) (Ab)using get_called_class() to extract the called namespace, test that the corresponding Helper
class exists, and use its $Value.
c) Dependency injection, which sounds like the best solution to whatever you're trying to do.
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[2014-11-23 23:03:31] llmll at gmx dot de
Sorry to say, but you did not understand the example provided. Please go through it again and find
that it has nothing to do with late static binding.
Your suggestion is invalid. A static::$Value is not defined, as we want the $Value property of a
different class: \Alpha\Helper. So we access it as Helper::$Value.
And here comes the problem. When later both classes are inherited / copied to \Beta namespace, the
Helper::$Value readout still accesses \Alpha\Helper::$Values, but it should be using
\Beta\Helper::$Value.
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[2014-11-23 22:35:30] requinix@php.net
LSB happens with the static keyword, not class names. Classes always resolve according to the
namespace of the code being executed (or by use statements), not some kind of contextual namespace
dependent on where the code is being executed.
echo static::$Value;
Don't forget that trying to access an undefined static property will fatal.
------------------------------------------------------------------------
[2014-11-23 21:50:26] llmll at gmx dot de
Description:
------------
Since PHP 5.3 we have late static binding to get a static variable from the actually instantiated
class type instead of the declared type. This is an important feature, but it does not take into
account a change in namespace. If the inheriting class lives in another namespace the wrong value is
taken.
If inside a namespace a class uses a peer class by its relative name, and later both classes are
derived in another namespace, all accesses go to the original namespace where the class was declared
in the first place.
Neccessary would be a late (runtime) namespace resolution for class names, the same was it works for
static::
Test script:
---------------
<?php
namespace Alpha;
class Base {
public static function Write() {
echo Helper::$Value;
}
}
class Helper {
public static $Value = "ALPHA";
}
namespace Beta;
class Base extends \Alpha\Base {
}
class Helper extends \Alpha\Helper {
public static $Value = 'BETA';
}
\Beta\Base::Write();
?>
Expected result:
----------------
As the exmple calls \Beta\Base::Write() in \Beta namespace one would expect the output to be
"BETA". The original static property is overwritten in Beta-namespace
The calls Helper::$Value should be call-context-sensitive. If called in namespace \Alpha it shoult
print "ALPHA" if called from a \Beta class, "BETA".
Actual result:
--------------
prints "ALPHA"
------------------------------------------------------------------------
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