Re: [PHP-DEV] deep compare: nesting level too deep
Moriyoshi Koizumi wrote: On Sat, Jan 25, 2003 at 01:00:53AM +0100, Vaclav Dvorak wrote: When I try to compare two "child" objects, PHP says: "Fatal error: Nesting level too deep - recursive dependency?". Well, yes, it _is_ a recursive dependency, but I don't see why PHP could not compare those objects anyway? Isn't it possible to tell whether two "names" reference the same "variable"? In fact, I'm comparing two references to the very same object, so the comparison could stop right there and not compare any members of the object. Are you trying it with ZE2? Compare those objects with "===" not "==". You'll get the exact result you've expected to see, I suppose. No, it's PHP 4.2.2. If it's working like this in ZE2, I guess I'm satisfied. Trying to backport it would just waste time that can be spent on ZE2. :-) EOT. Vaclav Dvorak <[EMAIL PROTECTED]> -- PHP Development Mailing List <http://www.php.net/> To unsubscribe, visit: http://www.php.net/unsub.php
[PHP-DEV] deep compare: nesting level too deep
Hello list,
I seem to have weird kinds of problems. I probably use some very unusual
ways to program. I wonder if it's good or bad. ;-)
I have an object that has a member variable that is an array whose
elements are references to other ("child") objects. Those child objects,
in turn, hold a reference to the "parent" object.
When I try to compare two "child" objects, PHP says: "Fatal error:
Nesting level too deep - recursive dependency?". Well, yes, it _is_ a
recursive dependency, but I don't see why PHP could not compare those
objects anyway? Isn't it possible to tell whether two "names" reference
the same "variable"? In fact, I'm comparing two references to the very
same object, so the comparison could stop right there and not compare
any members of the object.
Vaclav Dvorak <[EMAIL PROTECTED]>
PS: Any new ideas, opinions or fact on my foreach problem?
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Re: [PHP-DEV] foreach nastiness with references (bug #21702)
Moriyoshi Koizumi wrote: Moriyoshi Koizumi wrote: 1) Each time before entering a foreach loop, php first tries to make a copy of the array being iterated. 2) In case the array variable is either referenceing another variable or referenced by another variable, no copy is made here and the original array is used instead. Because of this behaviour, the original's internal array pointer increases in the loop eventually. Yes, I understand this. What I don't understand is WHY is it so? Why is foreach handling references specially? Why is your point 2) there? Oh, I found this issue was pointed out pretty long time ago. - Bug #5052 http://bugs.php.net/5052 - Bug #5270 (deleted?) http://news.php.net/article.php?group=php.dev&article=22668 http://news.php.net/article.php?group=php.dev&article=22672 http://news.php.net/article.php?group=php.dev&article=22673 [...] Anyway, please search the database first, in order not to post the same kind of bug twice. I did search the database, and indeed I did see that bug (#5052) before posting my bug report. In fact, if you read my bug report, you will see that I even mention this bug, and yet another one (#14607). The bug you now found (#5052) is similar but NOT the same. In fact, it describes the opposite behaviour: the reporter there says that nested foreach's on two COPIES of the same array don't work, and that he can work around the bug by making a reference to the array. In my bug, nested foreach on a copy works, but not on a reference. So there, I'm not such a complete idiot, you know. ;-) Regards, Vaclav Dvorak -- PHP Development Mailing List <http://www.php.net/> To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] foreach nastiness with references (bug #21702)
Moriyoshi Koizumi wrote: I tried to answer this question in the bug report page. [...] 1) Each time before entering a foreach loop, php first tries to make a copy of the array being iterated. 2) In case the array variable is either referenceing another variable or referenced by another variable, no copy is made here and the original array is used instead. Because of this behaviour, the original's internal array pointer increases in the loop eventually. Yes, I understand this. What I don't understand is WHY is it so? Why is foreach handling references specially? Why is your point 2) there? I probably don't see all the consequences (I know little about PHP/Zend internals and have found no documentation), but wouldn't the fix be as simple as changing the SEPARATE_ZVAL_IF_NOT_REF into SEPARATE_ZVAL on line 2251 of Zend/zend_execute.c? URL: http://lxr.php.net/source/php4/Zend/zend_execute.c#2251 (search for "case ZEND_FE_RESET:" if line numbers shift). BTW, what's the relation of http://lxr.php.net/source/php4/Zend/ and http://lxr.php.net/source/Zend/ ? Vaclav Dvorak <[EMAIL PROTECTED]> -- PHP Development Mailing List <http://www.php.net/> To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] foreach nastiness with references (bug #21702)
John Coggeshall wrote:
To answer part of your question:
What the documentation means is that
$val) {
$val = "newval";
}
?>
Will not change every element in the $foo array to "newval". However,
although $foo cannot be modified by modifying $key and $val the internal
array pointer WILL increment as if you were actually working on that
array directly.. So in order to restore the internal array pointer back
to the start of the array you'd need a call to reset($foo) first.
If that's what the documentation means, then the documentation is wrong.
Just try it. What you say is true ONLY when there's a reference to the
array, but that isn't mentioned in the docs. Cut'n'paste:
$a = array(1,2,3);
#$r =& $a;
echo "current before foreach: " . current($a) . "\n";
foreach($a as $b) {
echo "- value in cycle: " . $b . "\n";
echo "-- current in cycle: " . current($a) . "\n";
}
echo "current before foreach: " . current($a) . "\n";
?>
Try it, and the delete the hash mark and try again.
Regards,
Vaclav Dvorak
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[PHP-DEV] foreach nastiness with references (bug #21702)
Hi, there's a problem with foreach when the array it iterates over is a reference or has a reference: contrary to what was clearly written in the documentation for over two years until about two months ago, the foreach doesn't make a copy of the array, and so nested foreach's don't work because the inner foreach moves the array pointer to the end of the array already in the first iteration of the outer array. About two months ago, the documentation was changed, so that now it isn't obviously incorrect; rather, it is confusing. I think that the current foreach behaviour is seriously broken. Foreach should never tamper with the internal pointer of the array it iterates over, whether it is a reference or not. Nested foreach's should just work. I filed bug #21702 on this, but you people are way too quick on the wontfix trigger: one says Bogus without an explanation, after reopening another says Wontfix because of backwards compatibility. He may be right, of course, but I would expect some kind of a discussion. This _is_ an open source project, right? Obviously, the bugbase is not a good place for discussions, so I'll try it here. I, personally, find it hard to imagine how someone could knowingly write a script that depends on this broken, undocumented behaviour. Is there some way to find out? Surely there must have been questions like this before. How about releasing a corrected alpha release and seeing if anyone complains? One more thing: whether this bug is fixed or not, the documentation must be clarified! I don't know about you, but I simply don't understand what it's supposed to say. Quoting: "Note: Also note that foreach operates on a copy of the specified array, not the array itself, therefore the array pointer is not modified as with the each() construct and changes to the array element returned are not reflected in the original array. However, the internal pointer of the original array is advanced with the processing of the array. Assuming the foreach loop runs to completion, the array's internal pointer will be at the end of the array." Regards, Vaclav Dvorak <[EMAIL PROTECTED]> -- PHP Development Mailing List <http://www.php.net/> To unsubscribe, visit: http://www.php.net/unsub.php
