array_combine() converts boolean false keys to empty strings instead of integer keys #24254

Description

array_combine() converts a boolean false key to an empty string ("") instead of integer key 0, unlike normal PHP array-key conversion behavior.

Code to reproduce

<?php
var_dump(array_combine([true, false], ['true', 'false']));

Actual output

array(2) {
  [1]=>
  string(4) "true"
  [""]=>
  string(5) "false"
}

Expected output

array(2) {
  [1]=>
  string(4) "true"
  [0]=>
  string(5) "false"
}

Affected versions: PHP 8.4.x, PHP 8.5.x, PHP 8.6.x, and PHP 8.7.x

Additional information

Direct array construction converts boolean keys to integers:

var_dump([true => 'true', false => 'false']);

This suggests that array_combine() may be converting boolean keys to strings rather than applying the usual PHP array-key conversion rules.

PHP Version

PHP 8.4.26-dev (cli) (built: Oct 11 2026 12:44:08) (NTS DEBUG)
Copyright (c) The PHP Group
Zend Engine v4.4.26-dev, Copyright (c) Zend Technologies

Operating System

No response