Cached Iterator wrapper over iterators that does not support rewinding, like a Generator that emits value objects.

CachedNotRewindableIteratorAggregate.php

<?php

class CachedNotRewindableIteratorAggregate implements IteratorAggregate {
    private Iterator $iterator;
    private array $cache = [];
    public function __construct(Iterator $iterator) {
        $this->iterator = $iterator;
    }
    public function getIterator(): Iterator {
        $index = 0;
        while (isset($this->cache[$index]) || $this->iterator->valid()) {
            if (isset($this->cache[$index])) {
                [$key, $value] = $this->cache[$index];
            } else {
                $key = $this->iterator->key();
                $value = $this->iterator->current();
                $this->cache[$index] = [$key, $value];
                $this->iterator->next();
            }
            $index++;
            yield $key => $value;
        }
    }
}

EagerCachedNotRewindableIteratorAggregate.php

<?php

class EagerCachedNotRewindableIteratorAggregate implements IteratorAggregate {
    private array $cache = [];
    public function __construct(iterable $iterable) {
        foreach ($iterable as $key => $value) {
            $this->cache[$index] = [$key, $value];
        }
    }
    public function getIterator(): Iterator {
        $index = 0;
        while (isset($this->cache[$index])) {
            [$key, $value] = $this->cache[$index++];
            yield $key => $value;
        }
    }
}