Execute stream_filter_append user filters via php_user_filter brigades (#14001)

[PurHur]

Summary

• Implement VM execution for stream_filter_register() + stream_filter_append() user filters (Stdlib: stream_filter_append()/stream_filter_prepend() user filters not supported (LogicException) #14001)
• VmStreamFilterChain instantiates php_user_filter subclasses, runs filter() with brigades, and applies transformed bytes on read/write
• Fix brigade bucket sync: stream_bucket_append() now copies mutated data from bucket objects back into brigade storage
• Add datalen on bucket stdClass objects; use Variable::toObject() in brigade helpers (private $object access)

PHP-in-PHP: all logic in ext/standard/ (VmStreamFilterChain, VmStreamBucket, VmStreamFilters); no new C in runtime/.

Closes #14001

php-src reference

• ext/standard/streamsfuncs.c — stream_filter_append / stream_filter_prepend
• main/streams/filter.c — user filter plumbing

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php test/repro/maintainer_gap_stream_user_filter_uppercase.php
php bin/vm.php test/repro/maintainer_gap_stream_user_filter_uppercase.php'

Output (both):

HELLO

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
vendor/bin/phpunit --filter stream_user_filter_append
vendor/bin/phpunit --filter VmStreamFilterChainTest'

OK (2 tests, 2 assertions)   # stream_user_filter_append VM+JIT
OK (4 tests, 14 assertions)  # VmStreamFilterChainTest

Made with Cursor