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Next index for array returned from array_keys() is wrong #23576
Description
Description
The following code:
<?php
$a = array(123 => 123);
unset($a[123]);
$b = array_keys($a);
$b[] = 42;
var_dump($b);Resulted in this output:
array(1) {
[124]=>
int(42)
}
But I expected this output instead:
array(1) {
[0]=>
int(42)
}
The behavior changed during a patch version update: https://3v4l.org/KR2JQ#veol
This only happens when array_keys() is provided with an empty array that previously contained some elements.
PHP Version
PHP 8.4.25 (cli) (built: Aug 28 2026 07:36:03) (NTS)
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Zend Engine v4.4.25, Copyright (c) Zend Technologies
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Operating System
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Activity
[-]Next index for array returned from `array_keys()` ist wrong[/-][+]Next index for array returned from `array_keys()` is wrong[/+]Add empty array cases to the phpGH-23576 test
Fix phpGH-23576: array_keys() on an empty array returns a non-zero ne…
Merge branch 'PHP-8.4' into PHP-8.5
Merge branch 'PHP-8.5'