php: Always losing item #1 in ArrayIterator with using ArrayIterator::offsetUnset for a current element in loop

Question

I'm always losing second item (#1) in forearh of ArrayIterator and removing each element.

$cnt = 0;
$a = new ArrayIterator();
$a->append(++$cnt);
$a->append(++$cnt);
$a->append(++$cnt);
$a->append(++$cnt);
$a->append(++$cnt);

foreach ($a as $i => $item) {
    print_r("$i => $item".PHP_EOL);
    $a->offsetUnset($i);
}
print_r('count: '.$a->count().PHP_EOL);

foreach ($a as $i => $item) {
    print_r("lost! $i => $item".PHP_EOL);
}

Output:

0 => 1
2 => 3
3 => 4
4 => 5
count: 1
lost! 1 => 2

How it's possible? oO

$ php -v
PHP 5.5.37 (cli) (built: Jun 22 2016 16:14:46)
Copyright (c) 1997-2015 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2015 Zend Technologies

Pieter van den Ham · Accepted Answer · 2016-07-22 13:16:06Z

1

Congratulations! You have found a documented bug in ArrayIterator

Extract:

ArrayIterator always skips the second element in the array when calling offsetUnset(); on it while looping through.

Using the key from iterator and unsetting in the actual ArrayObject works as expected.

answered Jul 22, 2016 at 13:16

Pieter van den Ham

4,5153 gold badges28 silver badges41 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Kirby Over a year ago

Well, thanks for spotting the bug. I didn't know about it.

Kirby · Accepted Answer · 2016-07-22 13:12:52Z

0

Seem, there is the only to exhaust ArrayIterator with method offsetUnset. That's using do..while:

do {
    print_r("{$a->key()} => {$a->current()}".PHP_EOL);
    $a->offsetUnset($a->key());
} while ($a->count());
print_r('count: '.$a->count() . PHP_EOL);

Output:

0 => 1
1 => 2
2 => 3
3 => 4
4 => 5
count: 0

answered Jul 22, 2016 at 13:12

Kirby

3,1273 gold badges36 silver badges49 bronze badges

Collectives™ on Stack Overflow

php: Always losing item #1 in ArrayIterator with using ArrayIterator::offsetUnset for a current element in loop

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related