Re: [PHP] DOMNode children iteration (was Re: array() returns something weird)
Martin Scotta wrote: Fatal error: Call to a member function getAttribute() on a non-object in testme.php on line *121* Yes, this is _how_ the unmodified script errors out. It is not shown in the output I attached in my previous message because display_errors is Off in my php.ini, and the line that sets it to On in my script is commented out. I'm using a Apache/2.2.3 (Win32) PHP/5.2.6 I am not using Apache at all. The same error can be seen when I run the script directly through php on the command line. Is the script correctly? I have removed the in the loop I know that iterating a DOMNode's children using firstChild and nextSibling by reference causes trouble, thank you. The problem is that it causes trouble with objects unrelated to the loop itself, e.g. to variables defined _after_ the loop has terminated. and the script returns the attached file. Do you mean it returns what is in the output file _I_ have attached, or did _you_ try to attach something? If that is the case, then your attachment didn't get through. It looks like a bogus bug? I am certain it _is_ a genuine bug. For example, in PHP when you write: $foo = array(); echo gettype($foo); the output should not be NULL, but in my example script (unmodified, with iteration by reference) things like this start happening at some point. Regards, Szczepan Hołyszewski -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
RE: [PHP] DOMNode children iteration (was Re: array() returns something weird)
-Original Message- From: Szczepan Hołyszewski [mailto:webmas...@strefarytmu.pl] Sent: 26 August 2009 08:48 Martin Scotta wrote: Fatal error: Call to a member function getAttribute() on a non- object in testme.php on line *121* Yes, this is _how_ the unmodified script errors out. It is not shown in the output I attached in my previous message because display_errors is Off in my php.ini, and the line that sets it to On in my script is commented out. I'm using a Apache/2.2.3 (Win32) PHP/5.2.6 I am not using Apache at all. The same error can be seen when I run the script directly through php on the command line. Is the script correctly? I have removed the in the loop I really can't see why you'd want to use references in the posted loop anyway -- it's not likely to gain you any performance, and, as I understand it, may actually run more slowly than the non-reference version. I know that iterating a DOMNode's children using firstChild and nextSibling by reference causes trouble, thank you. The problem is that it causes trouble with objects unrelated to the loop itself, e.g. to variables defined _after_ the loop has terminated. I don't think it's possible to answer this for sure without seeing more of the code -- at least the complete body of the loop, plus as far as any further use of the variable $child (and any other variables assigned from it). Cheers! Mike -- Mike Ford, Electronic Information Developer, Libraries and Learning Innovation, Leeds Metropolitan University, C507, Civic Quarter Campus, Woodhouse Lane, LEEDS, LS1 3HE, United Kingdom Email: m.f...@leedsmet.ac.uk Tel: +44 113 812 4730 To view the terms under which this email is distributed, please go to http://disclaimer.leedsmet.ac.uk/email.htm
Re: [PHP] DOMNode children iteration (was Re: array() returns something weird)
I really can't see why you'd want to use references in the posted
loop anyway -- it's not likely to gain you any performance, and, as
I understand it, may actually run more slowly than the
non-reference version.
The why is irrelevant. It is perfectly legal PHP, and while it might be
illegal usage of DOMNode, it should only break the DOMNode, and not PHP
execution environment.
I don't think it's possible to answer this for sure without seeing more of
the code -- at least the complete body of the loop, plus as far as any
further use of the variable $child (and any other variables assigned from
it).
OK, I modified the example to show the problem _very_ directly. I commented out
the recursion-tracing echos, and added this code in renderObject() below the
if() that chooses between the good and evil loop, which means that the added
code is always executed immediately after the loop:
$x=array();
$y=y;
$z=1;
var_dump($xy,$y,$z);
echo \n;
Note that these variables:
- are first defined at this point
- are initialized immediately
- are initialized with immediate data (empty array and two scalars), not
with results of prior computation
- are never used or changed except for being dumped
- don't get any references to them created
Therefore one must expect that var_dump will always dump this:
array(0) {
}
string(1) y
int(1)
However it sometimes dumps this:
NULL
NULL
NULL
Best regards,
Szczepan Holyszewski
attachment: testme.php
--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] DOMNode children iteration (was Re: array() returns something weird)
-- Forwarded message --
From: Martin Scotta martinsco...@gmail.com
Date: Tue, Aug 25, 2009 at 6:24 PM
Subject: Re: [PHP] DOMNode children iteration (was Re: array() returns
something weird)
To: webmas...@strefarytmu.pl
Fatal error: Call to a member function getAttribute() on a non-object in
testme.php on line *121*
I'm using a Apache/2.2.3 (Win32) PHP/5.2.6
Is the script correctly? I have removed the in the loop and the script
returns the attached file.
It looks like a bogus bug?
2009/8/24 Szczepan Hołyszewski webmas...@strefarytmu.pl
Hi Lars and list!
New facts about the strange bug initially diagnosed as array() returning
NULL:
Firstly, the issue is not really about array() returning null, but about
full
blown UndefinedBehavior(TM) progressively trashing local variables. It just
so
happened that I noticed it first with a variable to which array() had been
assigned just before things began breaking.
Secondly, I proudly present the culprit: things break when I iterate over a
DOMNode's children *by reference* using firstChild and nextSibling:
for($child=$node-firstChild; $child; $child=$child-nextSibling)
{
//processing...
}
No problems if iteration is done by value or by DOMNodeList (childNodes,
DOMXPath...).
HOWEVER,
I still consider this a bug because it destablizes PHP. After the evil loop
has finished, things happen that should never happen, like a variable being
NULL immediately after being assigned array().
I attach a demonstration. It is a self-contained commented script that you
can
execute from command line. Also attached is output on my machine.
Best regards,
Szczepan Hołyszewski
--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
--
Martin Scotta
--
Martin Scotta
--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] DOMNode children iteration (was Re: array() returns something weird)
Hi Lars and list!
New facts about the strange bug initially diagnosed as array() returning NULL:
Firstly, the issue is not really about array() returning null, but about full
blown UndefinedBehavior(TM) progressively trashing local variables. It just so
happened that I noticed it first with a variable to which array() had been
assigned just before things began breaking.
Secondly, I proudly present the culprit: things break when I iterate over a
DOMNode's children *by reference* using firstChild and nextSibling:
for($child=$node-firstChild; $child; $child=$child-nextSibling) {
//processing...
}
No problems if iteration is done by value or by DOMNodeList (childNodes,
DOMXPath...).
HOWEVER,
I still consider this a bug because it destablizes PHP. After the evil loop
has finished, things happen that should never happen, like a variable being
NULL immediately after being assigned array().
I attach a demonstration. It is a self-contained commented script that you can
execute from command line. Also attached is output on my machine.
Best regards,
Szczepan Hołyszewski
attachment: testme.php
THE GOOD WAY (DOMNodeList):
Recursion structure:
-render()
-render()
-render()
-
-render()
-
-
-
Transformation result:
Some text.
[object type='foo' name='bar'][param name='__default_content']
Some parameter text.
Some parameter text.
[object type='bar' name='nested'][param name='__default_content']
Some nested parameter text.
Some nested parameter text.
[object type='baz' name='deeply_nested'][param
name='__default_content']
[/param][param name='bold']true[/param][/object]
More nested parameter text
More nested parameter text
[/param][/object]
[/param][/object]
Some more text
Success!
THE MIXED WAY (DOMNodeList at outermost level, then firstChild/nextSibling by
ref):
Recursion structure:
-render()
-render()
-render()
-
-render()
-
-
-
Transformation result:
Some text.
[object type='foo' name='bar'][param name='__default_content']
Some parameter text.
Some parameter text.
__default_content[param
name='__default_content']__default_content[/param][/object]
[/param][/object]
Some more text
Is it really a success?
THE EVIL WAY (firstChild/nextSibling by ref):
Recursion structure:
-render()
-render()
-render()
-
-render()
-
--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
