Stdlib: SPL iterator wrappers — FilterIterator, LimitIterator, AppendIterator, … (ext/spl parity) #4546

Category

stdlib | runtime

Problem

Zend ships a family of SPL iterator wrapper classes used throughout frameworks and the standard library:

• FilterIterator / RecursiveFilterIterator
• LimitIterator
• AppendIterator
• InfiniteIterator
• NoRewindIterator
• ParentIterator
• MultipleIterator
• GlobIterator
• CachingIterator

This compiler has partial SPL coverage (SplFileObject, RecursiveIteratorIterator, ArrayIterator, … per #3330) but none of the wrapper classes above are registered. User code calling new FilterIterator(...) fails with unknown class.

php-src reference

• php/php-src ext/spl/spl_iterators.c
• php/php-src ext/spl/spl_iterators.stub.php
• Iterator protocol: Zend/zend_iterators.c

Repro (failure today)

<?php
declare(strict_types=1);
$it = new ArrayIterator([1, 2, 3, 4, 5]);
$limited = new LimitIterator($it, 1, 2);
foreach ($limited as $v) {
    echo $v, "\n";
}

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

Scope (this repo)

Implement real Iterator protocol delegation — no permanent internal_* shims.

Done when

• Repro LimitIterator foreach output matches Zend on VM
• FilterIterator with user accept() method filters elements like Zend
• AppendIterator chains two iterators in order
• ./script/ci-fast.sh --filter 'LimitIterator|FilterIterator|AppendIterator' green
• Rows added via script/capability-matrix.php

Related

• Stdlib: SPL core structures — ArrayObject / SplQueue / SplStack / SplObjectStorage (ext/spl parity) #3330 / Stdlib: SplFileObject / SplFileInfo — SPL file iteration OOP (ext/spl parity) #3293 (SplFileObject / SplFileInfo)
• Language: foreach — array/Traversable iteration semantics parity (Zend/zend_vm_def.h, zend_compile.c) #4431 (foreach Traversable semantics)
• Stdlib: iterator_to_array() — materialize Traversable/Generator (ext/spl parity) #3100 / Stdlib: iterator_to_array() — Iterator/IteratorAggregate Traversable objects (phase 2 of #3100) #4244 (iterator_to_array Traversable phase 2)
• North star: Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492