FAQ

What package name should I install?

Install fast-forward/iterators :

composer require fast-forward/iterators

The package name should match the value declared in composer.json .

Which class should I try first?

Start with ChunkedIteratorAggregate if you need batches, SlidingWindowIteratorIterator if you need overlapping groups, or ClosureIteratorIterator if you simply want to transform values lazily.

Do I need to wrap arrays in ArrayIterator first?

No. Most public classes accept plain arrays directly. Internally, the package uses IterableIterator to normalize arrays and traversables into consistent iterators.

Why are some keys renumbered?

Several iterators intentionally expose normalized sequential keys because the original key layout no longer makes sense after combination or filtering.

Examples:

• ChainIterableIterator exposes sequential numeric positions;
• UniqueIteratorIterator exposes the position of each unique value;
• SlidingWindowIteratorIterator exposes the position of each window.

Why does ZipIteratorIterator stop before the longest input ends?

Because zip semantics are lockstep semantics. A row can only be produced while every input still has a current value, so the shortest iterable defines the maximum output length.

Why did SlidingWindowIteratorIterator return no values?

That happens when the input contains fewer elements than the window size. A window is only valid when it is completely full.

What is the difference between GroupByIteratorIterator and ConsecutiveGroupIterator ?

GroupByIteratorIterator groups all matching values across the entire input. ConsecutiveGroupIterator only groups neighbors while a callback keeps returning true .

How do I reuse a generator across multiple loops?

Use GeneratorRewindableIterator when you want a direct iterator, or GeneratorCachingIteratorAggregate when an aggregate-style wrapper fits your API better. Both strategies cache generated values so you can iterate again.

How do I inspect what an iterator is producing?

Use debugIterable() during development. It prints a section header, the count, and each visible key-value pair in a readable format.

Can my closure see iterator keys?

Yes. ClosureIteratorIterator calls your closure with both the current value and the current key, so you can transform based on either.

Does count() consume my iterator?

The package is designed so that countable wrappers count safely whenever possible. The exact strategy depends on the wrapped iterator, which is why the base classes in Foundations and Extension Points are worth reusing in custom code.

Can I build my own iterators on top of this package?

Yes. The recommended starting points are CountableIteratorAggregate , CountableIteratorIterator , CountableFilterIterator , and CountableIterator . The Extending the Library page explains when to use each one.

Do I need a framework or container integration?

No. This package is framework-agnostic. Instantiate the iterators directly, or register them in your own container exactly like any other PHP object.