ID: 16227
Updated by: [EMAIL PROTECTED]
Reported By: [EMAIL PROTECTED]
Status: Open
Bug Type: Documentation problem
Operating System: ANY
PHP Version: PHP4 only
New Comment:
each() as a function does not know in which context it was called so it
just returns the 'current' element and advances the internal position
pointer, very similar to the java next_element() iterator (hope i got
the name right). when no more elements are left it returns false until
being reset
each() can not know that it was called from different loop runs so it
will return false forever until reset. one might
think about auto-reseting it after returning false once, but backwards
compatibility will be in our way once again here
the problem does not happen this way in java because there
next_element() advances the internal pointer before returning values
and you have to use first_element() to get
the first one (which implies a reset)
foreach uses a private copy of the array structure so it has its own
internal pointer which is recreated for every foreach instance so the
problem does occure here
Previous Comments:
------------------------------------------------------------------------
[2002-03-23 20:44:45] [EMAIL PROTECTED]
Oops,
$arr = array('a', 'b', 'c');
does reset position :)
------------------------------------------------------------------------
[2002-03-23 20:39:56] [EMAIL PROTECTED]
Both each() and foreach() uses internal hash position variable.
Difference is foreach() reset internal hash position to the first
element while each() does not.
A problematic behavior is an assignment resets internal hash
position. There are other cases programmer has to be careful about
internal hash position and reference counting feature.
In addition to that, it is _not_ intuitive that assignment as follows
$arr = array('a', 'b', 'c');
does not reset hash posiiton, while following assignment does reset
hash position.
$arr2 = $arr1;
Anyway, some internal hash posision behaviors are inconsistent and
_not_ intuitive at all. This would be really hard to find if a user
experience the problem. Therefore, it should be documented :)
------------------------------------------------------------------------
[2002-03-23 07:44:26] [EMAIL PROTECTED]
OK, as a newbie PHP-er (experienced with Perl and Java) the
documentation I've been using suggested using that example before
foreach(). The foreach() behavior is free from the problem it seems,
even though documentation for foreach() on php.net claims that they
should be equivalent.
Can anyone explain to this newbie why the (while list each) version was
the "intended behavior"? Of course, having to use reset() seems kind
of odd to me anyway, but I wonder what was "wrong" with my first
code... PHP seems to look like it has Perl's "more than one way to do
it", but only in very limited areas. (I suppose if push came to shove I
could go back to using my own array walkers, but still...)
------------------------------------------------------------------------
[2002-03-23 07:10:07] [EMAIL PROTECTED]
Ok. Then this is documentation problem.
(I would like to hear from Andi or Zeev, though)
There should be note that internal hash position is reset if value is
assigned. (Both LVALUE and RVLAUE. They are the same value anyway.)
Also, reference counting side effect should be documented fully.
BTW, to fix this misbihavior, we need a additional variable to keep
track of hash position for each zval. (and change related codes) PHP3
does not have problem, since it does not have reference counting.
------------------------------------------------------------------------
[2002-03-23 06:46:24] [EMAIL PROTECTED]
It's not a flaw, it's designed like this.
Derick
------------------------------------------------------------------------
The remainder of the comments for this report are too long. To view
the rest of the comments, please view the bug report online at
http://bugs.php.net/16227
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Edit this bug report at http://bugs.php.net/?id=16227&edit=1
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