Regression: stream_filter_register() non-php_user_filter class — returns false, Zend returns true + E_WARNING (ext/standard/streams.c) #13733

Category

stdlib · php-src-strict

Problem

When stream_filter_register() is called with a class that does not extend php_user_filter, Zend emits E_WARNING (class must extend php_user_filter) and returns true — the filter name is registered and appears in stream_get_filters(). The VM returns false, does not register the name, and subsequent stream_filter_append() is a no-op.

This diverges from php-src stream user-filter registration semantics and breaks code that checks the boolean return while still expecting Zend’s warning side effect.

php-src reference

• php/php-src ext/standard/streams.c — php_stream_filter_register_factory
• php/php-src ext/standard/user_filters.c — php_user_filter base class requirement

Repro (verified 2026-06-29)

php test/repro/stream_filter_register_invalid_class_return.php
php bin/vm.php test/repro/stream_filter_register_invalid_class_return.php

Minimal:

class BadFilter {
    public function filter($in, $out, &$consumed, $closing) {
        return PSFS_PASS_ON;
    }
}
$name = 'bad.' . getmypid();
$ok = stream_filter_register($name, BadFilter::class);
// Zend: $ok === true; VM: $ok === false

Scope (PHP-in-PHP first)

Done when (php-src-strict)

• Invalid class: E_WARNING + return true like Zend
• Filter name listed in stream_get_filters() after register attempt
• Valid extends php_user_filter path unchanged (test/repro/maintainer_gap_php_user_filter_class.php stays green)
• ./script/ci-fast.sh --filter stream_filter_register green

Verification

php test/repro/stream_filter_register_invalid_class_return.php
php bin/vm.php test/repro/stream_filter_register_invalid_class_return.php

Links

• Stdlib: stream_bucket_make_writeable() / stream_bucket_append() — filter brigades (streamsfuncs.c) #4688 stream buckets · North star Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492