Everything

php

protected/private function __construct() not allowed in 5.0.4?

php.internals

Greg Beaver

21 years ago

Hi all,

I just spent quite a while searching the archives, and can't find any
explanation of why this code worked in 5.0.3 but doesn't in 5.0.4:

<?php
class blah {
protected function __construct(){}
}
?>

Could someone please enlighten me?  I was using this for a singleton
pattern, and so it would be nice to know why it is so critical for the
engine to be anal retentive here.  It seems to me that it should be up
to the programmer to decide how easily the object can be instantiated,
unless there is a deeper engine stability issue.

Thanks,
Greg

Marcus Boerger

21 years ago

Hello Greg,

Wednesday, April 20, 2005, 5:11:46 AM, you wrote:

> Hi all,

> I just spent quite a while searching the archives, and can't find any
> explanation of why this code worked in 5.0.3 but doesn't in 5.0.4:

> <?php
> class blah {
>      protected function __construct(){}
> }

?>>

> Could someone please enlighten me?  I was using this for a singleton
> pattern, and so it would be nice to know why it is so critical for the
> engine to be anal retentive here.  It seems to me that it should be up
> to the programmer to decide how easily the object can be instantiated,
> unless there is a deeper engine stability issue.

> Thanks,
> Greg

At least it works for 5.0.5-dev:
marcus@zaphod /usr/src/php-cvs $ php -r 'class T { protected function __construct() {} static function test() { return new T;} } var_dump(T::test());'
make: `sapi/cli/php' is up to date.
object(T)#1 (0) {
}
marcus@zaphod /usr/src/php-cvs $ ../PHP_5_0/sapi/cli/php -r 'class T { protected function __construct() {} static function test() { return new T;} } var_dump(T::test());'
object(T)#1 (0) {
}
marcus@zaphod /usr/src/php-cvs $ ../PHP_5_0/sapi/cli/php -v
PHP 5.0.5-dev (cli) (built: Apr  7 2005 17:24:12) (DEBUG)
Copyright (c) 1997-2004 The PHP Group
Zend Engine v2.0.4-dev, Copyright (c) 1998-2004 Zend Technologies

but i currently cannot reproduce it with 5.0.4, sorry.

--
Best regards,
Marcus                            mailto:mail@marcus-boerger.de

Antony Dovgal

21 years ago

On Tue, 19 Apr 2005 23:11:46 -0400
Greg Beaver <cellog@php.net> wrote:

> Hi all,
>
> I just spent quite a while searching the archives, and can't find any
> explanation of why this code worked in 5.0.3 but doesn't in 5.0.4:
>
> <?php
> class blah {
>      protected function __construct(){}
> }
> ?>

Works fine with HEAD, 5.0.5-dev & 5.0.4.
Could you plz explain what did you mean when you said "doesn't work" ?

--
Wbr,
Antony Dovgal aka tony2001
antony@zend.com

Greg Beaver

21 years ago

Antony Dovgal wrote:

>On Tue, 19 Apr 2005 23:11:46 -0400
>Greg Beaver <cellog@php.net> wrote:
>
>
>
>>Hi all,
>>
>>I just spent quite a while searching the archives, and can't find any
>>explanation of why this code worked in 5.0.3 but doesn't in 5.0.4:
>>
>><?php
>>class blah {
>>     protected function __construct(){}
>>}
>>?>
>>
>>
>
>Works fine with HEAD, 5.0.5-dev & 5.0.4.
>Could you plz explain what did you mean when you said "doesn't work" ?
>

I didn't read the error message closely enough - when extending the base
class, which has a public constructor, the protected keyword is no
longer allowed.

<b>Fatal error</b>:  Access level to
Chiara_PEAR_Server_Frontend_Xmlrpc5_Package
::__construct() must be public (as in class Chiara_XML_RPC5_Server) in
<b>c:\php
5\pear\Chiara\PEAR\Server\Frontend\Xmlrpc5.php</b> on line <b>40</b><br />

Try this code (which worked in 5.0.3)

<?php
class a { public function __construct(){}}
class b extends a { protected function __construct(){}}
?>

Greg

Johannes Schlueter

21 years ago

Hi Greg,

Greg Beaver wrote:

> Try this code (which worked in 5.0.3)
>
> <?php
> class a { public function __construct(){}}
> class b extends a { protected function __construct(){}}
> ?>

This was changed since such a change of visibility makes no sense - if you
extend a class it should still be compatible with it's parent class.

johannes

--
Johannes Schlüter                           Mayflower GmbH / ThinkPHP
http://thinkphp.de                            http://blog.thinkphp.de

Greg Beaver

21 years ago

Johannes Schlueter wrote:

> Hi Greg,
>
> Greg Beaver wrote:
>
>
>>Try this code (which worked in 5.0.3)
>>
>><?php
>>class a { public function __construct(){}}
>>class b extends a { protected function __construct(){}}
>>?>
>
>
> This was changed since such a change of visibility makes no sense - if you
> extend a class it should still be compatible with it's parent class.

I highly recommend removing this restriction for constructors.  The
programmer should be the one to determine whether this makes sense.  For
other methods that are not instance-dependent, this restriction makes
perfect sense.  most methods can be called by any instance without
needing to know what the class is.  constructors are not like this.
They are tightly bound to the specific class they are in.  The same
reasoning was used to remove the restrictions on constructor arguments -
constructors are not normal methods.

I am extending a general purpose XML_RPC server implementation which is
designed to be instance based, and making it a singleton.  There is
nothing wrong with this, and object instances are still 100% compatible.

Nobody in their right mind expects to be able to instantiate a child
class without knowing anything about it - each class does something
unique and possibly incompatible with the base class, otherwise there
would be no point in extending the base class.

This seems a case of PHP trying to prevent me from doing logic errors
without knowing anything about the code, i.e. not in the PHP spirit.

Greg

Antony Dovgal

21 years ago

On Wed, 20 Apr 2005 09:52:25 -0400
Greg Beaver <greg@chiaraquartet.net> wrote:

> Antony Dovgal wrote:
>
> >On Tue, 19 Apr 2005 23:11:46 -0400
> >Greg Beaver <cellog@php.net> wrote:
> >
> >
> >
> >>Hi all,
> >>
> >>I just spent quite a while searching the archives, and can't find any
> >>explanation of why this code worked in 5.0.3 but doesn't in 5.0.4:
> >>
> >><?php
> >>class blah {
> >>     protected function __construct(){}
> >>}
> >>?>
> >>
> >>
> >
> >Works fine with HEAD, 5.0.5-dev & 5.0.4.
> >Could you plz explain what did you mean when you said "doesn't work" ?
> >
>
> I didn't read the error message closely enough - when extending the base
> class, which has a public constructor, the protected keyword is no
> longer allowed.
>
> <b>Fatal error</b>:  Access level to
> Chiara_PEAR_Server_Frontend_Xmlrpc5_Package
> ::__construct() must be public (as in class Chiara_XML_RPC5_Server) in
> <b>c:\php
> 5\pear\Chiara\PEAR\Server\Frontend\Xmlrpc5.php</b> on line <b>40</b><br />
>
> Try this code (which worked in 5.0.3)
>
> <?php
> class a { public function __construct(){}}
> class b extends a { protected function __construct(){}}
> ?>

It doesn't work in 5.0.3 too:
---------
#./sapi/cli/php -v
PHP 5.0.3 (cli) (built: Apr 20 2005 18:26:52) (DEBUG)
Copyright (c) 1997-2004 The PHP Group

#./sapi/cli/php /www/index.php

Fatal error: Access level to b::__construct() must be public (as in class a) in /www/index.php on line 4
---------

As far as I can see this change first appeared somewhere in late 2002, because this patch: http://cvs.php.net/diff.php/ZendEngine2/zend_compile.c?r1=1.337&r2=1.338&ty=u
fixes it.

--
Wbr,
Antony Dovgal aka tony2001
antony@zend.com