# Bug #27782

- Thread: https://externals.io/message/8876
- Original archive: https://news-web.php.net/php.internals/8876
- Started by Ilia Alshanetsky on 2004-04-01T19:24:25+00:00
- Messages: 3
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## #8876 — Ilia Alshanetsky — 2004-04-01T19:24:25+00:00

URL: https://externals.io/message/8876#8876

This bug is the result of the engine moving the current array position to 0x0 
if there are no more next elements (next/each) or no more preceding elements 
(prev). The results is that if you were to run:
<?php
$a = array(1,2,3);
while(next($a));
echo prev($a);
?>
the out would be `NULL` rather then 2. The fix that I just reverted from PHP4 
addresses this problem for the 3 functions involved, but has a BC issue. 
Before the patch since the array position was pointing to 0x0 functions like 
 `key()` that depend on the position would return FALSE/NULL, now they end up 
returning the first or last element depending on wether next or prev was used 
to iterate through the array. This is why I decided to revert the patch for 
4.3.X.
For PHP 5 we need to decide wether we want to keep the patch with the changes 
it introduces. Revert it and assume the old behavior as correct or to add a 
flag/option that would detect this condition. Allowing the old functionality 
to be maintained but also make it possible to allow the example above to work 
correctly.

Ilia

---

## #8877 — Marcus Boerger — 2004-04-01T19:56:50+00:00

URL: https://externals.io/message/8876#8877 · In reply to: #8876

Hello Ilia,

Thursday, April 1, 2004, 9:24:25 PM, you wrote:

> This bug is the result of the engine moving the current array position to 0x0
> if there are no more next elements (next/each) or no more preceding elements
> (prev). The results is that if you were to run:
> <?php
> $a = array(1,2,3);
> while(next($a));
> echo prev($a);
?>>
> the out would be `NULL` rather then 2. The fix that I just reverted from PHP4
> addresses this problem for the 3 functions involved, but has a BC issue. 
> Before the patch since the array position was pointing to 0x0 functions like
> `key()` that depend on the position would return FALSE/NULL, now they end up
> returning the first or last element depending on wether next or prev was used
> to iterate through the array. This is why I decided to revert the patch for
> 4.3.X.
> For PHP 5 we need to decide wether we want to keep the patch with the changes
> it introduces. Revert it and assume the old behavior as correct or to add a
> flag/option that would detect this condition. Allowing the old functionality
> to be maintained but also make it possible to allow the example above to work
> correctly.

Sidenote: A while back i wanted to have array_has_more() which would now
be array_valid() or just valid().

Without that mentioned test we depend on key(@eof) -> false|NULL because
next(@eof) -> false|NULL has the sideeffect that it either must be
disallowed to store false|NULL or that it simply won't work. The patch
drops the necessary behavior for `key()` [now disallow storing false|NULL?].

Generally i would like to have the same set of functions available for
arrays we have for iterators. That would add valid(). When we have this
we could also adapt the logic most people would implement - access after
last elemet [when valid()===false] leads to undefined - in other words
the behavior of `key()`/next() is irrelevant.

Test script:
$ php -r '$a=array(1,2);var_dump($a);var_dump(key($a));var_dump(next($a));var_dump(key($a));var_dump(next($a));var_dump(key($a));'
array(2) {
  [0]=>
  int(1)
  [1]=>
  int(2)
}
int(0)          // key(@0)
int(2)          // next(@0)
int(1)          // key(@1)
bool(false)     // next(@1)
int(1)          // key(@eof)  we need retval false|NULL or we need valid()

regards
marcus

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## #8878 — Andi Gutmans — 2004-04-01T20:34:17+00:00

URL: https://externals.io/message/8876#8878 · In reply to: #8876

I'm not sure these functions should be fixed. Personally I always recommend 
to people to use foreach() or sometimes each() but never these old 
functions. If the only problem is that once we reach the end, we can't call 
 `prev()` then I think we should just document this. Using array_valid() in 
conjunction with the shorter `next()`, `prev()`, `current()` might look a bit odd 
but it's something we could do. The question is if it's really worth it.


At 09:56 PM 4/1/2004 +0200, Marcus Boerger wrote:
>Hello Ilia,
>
>Thursday, April 1, 2004, 9:24:25 PM, you wrote:
>
> > […]
> to 0x0
> > […]
> elements
> > […]
>?>>
> > […]
> like
> > […]
> was used
> > […]
> changes
> > […]
> functionality
> > […]
> to work
> > […]
>
>Sidenote: A while back i wanted to have array_has_more() which would now
>be array_valid() or just valid().
>
>Without that mentioned test we depend on key(@eof) -> false|NULL because
>next(@eof) -> false|NULL has the sideeffect that it either must be
>disallowed to store false|NULL or that it simply won't work. The patch
>drops the necessary behavior for `key()` [now disallow storing false|NULL?].
>
>Generally i would like to have the same set of functions available for
>arrays we have for iterators. That would add valid(). When we have this
>we could also adapt the logic most people would implement - access after
>last elemet [when valid()===false] leads to undefined - in other words
>the behavior of `key()`/next() is irrelevant.
>
>Test script:
>$ php -r 
>'$a=array(1,2);var_dump($a);var_dump(key($a));var_dump(next($a));var_dump(key($a));var_dump(next($a));var_dump(key($a));'
>array(2) {
>   [0]=>
>   int(1)
>   [1]=>
>   int(2)
>}
>int(0)          // key(@0)
>int(2)          // next(@0)
>int(1)          // key(@1)
>bool(false)     // next(@1)
>int(1)          // key(@eof)  we need retval false|NULL or we need valid()
>
>regards
>marcus