EachPromise example

    public static function of(
        $iterable,
        callable $onFulfilled = null,
        callable $onRejected = null
    ): PromiseInterface {
        return (new EachPromise($iterable, [
            'fulfilled' => $onFulfilled,
            'rejected' => $onRejected,
        ]))->promise();
    }

    /** * Like of, but only allows a certain number of outstanding promises at any * given time. * * $concurrency may be an integer or a function that accepts the number of * pending promises and returns a numeric concurrency limit value to allow * for dynamic a concurrency size. * * @param mixed $iterable * @param int|callable $concurrency * @param callable $onFulfilled * @param callable $onRejected */

foreach ($iterable as $key => $rfn) {
                if ($rfn instanceof RequestInterface) {
                    yield $key => $client->sendAsync($rfn, $opts);
                } elseif (\is_callable($rfn)) {
                    yield $key => $rfn($opts);
                } else {
                    throw new \InvalidArgumentException('Each value yielded by the iterator must be a Psr7\Http\Message\RequestInterface or a callable that returns a promise that fulfills with a Psr7\Message\Http\ResponseInterface object.');
                }
            }
        };

        $this->each = new EachPromise($requests(), $config);
    }

    /** * Get promise */
    public function promise(): PromiseInterface
    {
        return $this->each->promise();
    }

    /** * Sends multiple requests concurrently and returns an array of responses * and exceptions that uses the same ordering as the provided requests. * * IMPORTANT: This method keeps every request and response in memory, and * as such, is NOT recommended when sending a large number or an * indeterminate number of requests concurrently. * * @param ClientInterface $client Client used to send the requests * @param array|\Iterator $requests Requests to send concurrently. * @param array $options Passes through the options available in * {@see \GuzzleHttp\Pool::__construct} * * @return array Returns an array containing the response or an exception * in the same order that the requests were sent. * * @throws \InvalidArgumentException if the event format is incorrect. */