Description:
------------
Referencing to SplFixedArray interrupts foreach loop.

Test script:
---------------
https://3v4l.org/FdN4i

Expected result:
----------------
3 iterations executed.

Actual result:
--------------
1 iteration executed.

Description:
------------
Referencing to SplFixedArray interrupts foreach loop.

Test script:
---------------
https://3v4l.org/FdN4i

Expected result:
----------------
3 iterations executed.

Actual result:
--------------
1 iteration executed.

Description:
------------
Referencing to SplFixedArray interrupts foreach loop.

Test script:
---------------
https://3v4l.org/FdN4i

Expected result:
----------------
3 iterations executed.

Actual result:
--------------
1 iteration executed.

Presuming for Iterators

    foreach ($it as $el) {
        var_dump($el);
    }

is equivalent to

    for ($it->rewind(); $it->valid(); $it->next()) {
        $el = $it->current();
        var_dump($el);
    }

the behavior is correct.  On the other hand, SplDoublyLinkedList,
for instance, supports nested traversal via foreach ...

cmb@php.net, as far as SPLFixedArray implements Traversable, it is expected to support foreach.

I updated code, to make the difference more obvious:
https://3v4l.org/N9k7P

Please, note, that in the test code i provided, unless we use $collection->getSum() inside the loop - it works as expected.

Yes, a single foreach loop works certainly as expected; the
problem is *nesting* of foreach loops:

    <?php
    $spl = SplFixedArray::fromArray([0, 1]);
    foreach ($spl as $el1) {
        foreach ($spl as $el2) {
            echo "$el1.$el2\n";
        }
    }
    ?>

outputs

    0.0
    0.1

while you want to get

    0.0
    0.1
    1.0
    1.1

It seems to me that this behavior is correct for Iterators; maybe
not for IteratorAggregates.

SplFixedArray should probably be IteratorAggregate rather than Iterator...

I do think we should ensure that multiple parallel get_iterator()s are supported independently of that.

> I do think we should ensure that multiple parallel get_iterator()s are supported independently of that.

Nikita, I don't understand how SplFixedArray could possibly support multiple parallel get_iterator()s while still following the contract of the Iterator interface. Could you explain what you mean?

> Nikita, I don't understand how SplFixedArray could possibly support multiple
> parallel get_iterator()s while still following the contract of the Iterator
> interface. Could you explain what you mean?
To make sure that all the Traversables returned by multiple calls to getIterator() won't conflict with each other.

I have a patch which "fixes" get_iterator() without converting SplFixedArray to an IteratorAggregate. It's a pretty dubious idea. Still, I may push it to GH for review and comments.

The fix for this issue has been committed[1], and will be
available as of PHP 8.1.0 for BC reasons.

[1] <https://github.com/php/php-src/commit/4222ae16e7848e0b3f062a9a989d387de307a7af>

(Correction: This is fixed in 8.0.0, rather than 8.1.0.)