Stdlib: iterator_to_array() accepts array keys as "Array" — Zend TypeError Illegal offset type (ext/spl/iterator.c) #23573

Category

bug · php-src-strict · stdlib · iterator_to_array / MultipleIterator

Problem

When an iterator yields an array key (e.g. MultipleIterator with MIT_KEYS_ASSOC / MIT_KEYS_NUMERIC), Zend iterator_to_array() throws TypeError: Illegal offset type. The VM coerces the key to the string "Array" and returns a one-element array (last row only) — silent wrong result.

foreach over the same MultipleIterator correctly yields array keys on both Zend and VM; the gap is specifically materializing those keys into a PHP array.

Verified 2026-07-26 (host Zend 8.2.32 vs php bin/vm.php):

php-src reference

• php/php-src ext/spl/spl_iterators.c — iterator_to_array / spl_iterator_to_array_apply (array key → illegal offset)
• MultipleIterator key shape: same tree — MIT_KEYS_ASSOC / MIT_KEYS_NUMERIC

PHP implementation target

• lib/VM.php — iterator_to_array materialization must TypeError on non-int/non-string keys (reuse HashTable::normalizeIndexKey / EnumCaseSupport::rejectIllegalArrayOffset patterns already used elsewhere)
• Do not special-case MultipleIterator only — any Traversable with array/object keys should match Zend
• PHP-in-PHP; no new C runtime

Repro

./script/docker-exec.sh -- bash -lc 'cat > /tmp/ita_akey.php <<'\''PHP'\''
<?php
$m = new MultipleIterator(MultipleIterator::MIT_NEED_ALL | MultipleIterator::MIT_KEYS_ASSOC);
$m->attachIterator(new ArrayIterator([10, 20]), "a");
$m->attachIterator(new ArrayIterator([30, 40]), "b");
try {
    var_export(iterator_to_array($m));
    echo "\n";
} catch (Throwable $e) {
    echo get_class($e), ":", $e->getMessage(), "\n";
}
PHP
php /tmp/ita_akey.php; php bin/vm.php /tmp/ita_akey.php'

Done when

• iterator_to_array on MultipleIterator (ASSOC and NUMERIC key modes) throws TypeError: Illegal offset type like Zend
• foreach over the same iterators still yields array keys correctly
• Compliance .phpt guard under test/compliance/cases/stdlib/ (or SPL)
• php-src-strict; no php-compiler-strict shortcut