primes.php with IteratorAggregate

primes.php

<?php

/**
 * Run this code with: "php -n <file.php>" to make sure no configuration will be used
 * so xdebug will not be used either.
 */

declare(strict_types=1);

namespace App;

use Generator;
use Iterator;
use IteratorAggregate;

class PrimeGenerator implements IteratorAggregate
{
    private $iterator;

    public function __construct(Iterator $iterator)
    {
        $this->iterator = $iterator;
    }

    public function getIterator()
    {
        $this->iterator->next();

        yield $primeNumber = $this->iterator->current();

        yield from new PrimeGenerator(
            new \CallbackFilterIterator(
                $this->iterator,
                fn(int $a): bool => $a % $primeNumber !== 0
            )
        );
    }
}

function integerGenerator(int $init = 1, callable $succ): Generator
{
    yield $init;

    return yield from integerGenerator($succ($init), $succ);
}

$primes = new PrimeGenerator(integerGenerator(2, fn(int $n): int => $n + 1));

foreach ($primes as $p) {
    var_dump($p);
}