Stream Iterator oddity

stream-iterator.php

<?php

declare(strict_types=1);

namespace App;

use Generator;
use Iterator;

class ClosureIterator implements \Iterator
{
    /**
     * @var array<int, mixed>
     */
    private array $arguments;

    /**
     * @var callable
     */
    private $callable;

    public function __construct(callable $callable, ...$arguments)
    {
        $this->callable = $callable;
        $this->arguments = $arguments;
        $this->iterator = $this->getGenerator();
    }

    protected \Iterator $iterator;

    public function current()
    {
        return $this->iterator->current();
    }

    public function key()
    {
        return $this->iterator->key();
    }

    public function next(): void
    {
        $this->iterator->next();
    }

    public function valid(): bool
    {
        return $this->iterator->valid();
    }

    public function rewind(): void
    {
        $this->iterator = $this->getGenerator();
    }

    private function getGenerator(): Generator
    {
        $generator = static fn (callable $callable, array $arguments): \Generator => yield from ($callable)(...$arguments);

        return ($generator)($this->callable, $this->arguments);
    }
}

$string = 'Lorem ipsum dolor sit amet';
$stream = fopen('data://text/plain,' . $string, 'rb');

$callable = static function ($resource): \Generator {
    while (false !== $chunk = fgetc($resource)) {
        yield $chunk;
    }
};

// Test 1
$closureIterator = new ClosureIterator($callable, $stream);
$string1 = implode('', iterator_to_array($closureIterator)); // 'Lorem ipsum dolor sit amet'

// Test 2
$closureIterator = new ClosureIterator($callable, $stream);
$closureIterator->valid();
$string2 = implode('', iterator_to_array($closureIterator)); // 'orem ipsum dolor sit amet' <- Missing first letter! Why ?

var_dump($string1 === $string2); // false