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Posted by Jerry Stuckle on 05/20/07 02:35
ZeldorBlat wrote:
> On May 18, 10:44 pm, Jerry Stuckle <jstuck...@attglobal.net> wrote:
>> ZeldorBlat wrote:
>>> On May 18, 9:05 pm, Jerry Stuckle <jstuck...@attglobal.net> wrote:
>>>> ZeldorBlat wrote:
>>>>> On May 18, 11:40 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com>
>>>>> wrote:
>>>>>> "ZeldorBlat" <zeldorb...@gmail.com> wrote in message
>>>>>> news:1179501018.125313.63600@p77g2000hsh.googlegroups.com...
>>>>>>> On May 18, 11:05 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com>
>>>>>>> wrote:
>>>>>>>> Is it safe to remove elements from an array that foreach is working on?
>>>>>>>> (normally this is not the case but not sure in php) If so is there an
>>>>>>>> efficient way to handle it? (I could add the indexes to a temp array and
>>>>>>>> delete afterwards if necessary but since I'm actually working in a nested
>>>>>>>> situation this could get a little messy. I guess I could set there values
>>>>>>>> to
>>>>>>>> null and remove them afterwards?
>>>>>>>> Thanks,
>>>>>>>> Jon
>>>>>>> Why don't you try it and see what happens?
>>>>>> Um... cause I did... but that doesn't mean much. Just cause someone tries
>>>>>> something doesn't prove that it will always work like that...
>>>>>> got any more bright ideas?
>>>>>> Or is the question to hard for you?
>>>>> No, the question is not to (sic) hard for me. But, as you've already
>>>>> discovered, it isn't that difficult to test, either.
>>>> Sorry, I agree with Jon on this one.
>>>> I make it a habit not to delete entries in a foreach() loop. Rather, I
>>>> build an array of keys I want to delete, and after the loop ends, delete
>>>> the entries from my delete array.
>>>> I don't know whether an operation like this is guaranteed to work in PHP
>>>> - I've never seen it documented, so I suspect not. And just because it
>>>> works in one release under a certain set of conditions is not a
>>>> guarantee it will work on another release or under different conditions.
>>>> --
>>>> ==================
>>>> Remove the "x" from my email address
>>>> Jerry Stuckle
>>>> JDS Computer Training Corp.
>>>> jstuck...@attglobal.net
>>>> ==================
>>> I never said I disagreed with him -- in fact I, too, generally don't
>>> delete elements inside a foreach. However, I will say that when I
>>> have done it things seem to work as expected. I guess it all comes
>>> down to whether or not the array's internal pointer is modified when
>>> you unset the element it's pointing to (I suspect it isn't).
>>> I see a lot of questions in these newsgroups that look something like,
>>> "What happens if I do X?" or "In PHP is this code valid?" The point I
>>> was trying to make (and apparently Jon took offense to it) was that
>>> it's easy enough to just try it and see what happens. Software is
>>> just that: soft. It can be changed easily enough :)
>> Yes, and in a case like this that change can break his code.
>>
>> As I said - I've never seen it documented that this is valid. Maybe it
>> is and I missed it; I really don't know.
>>
>> But this isn't the same as a lot of other "try it and find out"
>> questions. In this case it's a known problem in other programming
>> languages, and if it is documented that this should or should not work,
>> no one has pointed anyone to it.
>>
>> And until I see something from the PHP developers saying it is OK, I
>> wouldn't do it.
>>
>> --
>> ==================
>> Remove the "x" from my email address
>> Jerry Stuckle
>> JDS Computer Training Corp.
>> jstuck...@attglobal.net
>> ==================
>
> This suggests that it's safe (from <http://www.php.net/foreach>):
>
> "Unless the array is referenced, foreach operates on a copy of the
> specified array and 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."
>
> So unsetting a value in the original array should not affect the copy
> that foreach is working on.
>
I read that as just the opposite - changes in the copy do not affect the
original array.
It doesn't say how often the copy is refreshed from the original array -
or when changes in the original are reflected in the copy.
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================
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