Learn how a ClockInterface helps you decouple time and write stable, testable code.

You can use the SPL LimitIterator, feed it the generator, and give it the offset and limit.

``` foreach (new LimitIterator($generator, 0, 3) as $value) { echo $value; } ```

https://www.php.net/manual/en/class.limititerator.php

Just to clarify my intent with posts like this:

I'm not suggesting that PHP is the ideal tool for every use case. The goal is to share a concept that might be unfamiliar to some developers, using PHP as the context.

Sometimes learning about a concept in a familiar language helps you recognise where it might be useful elsewhere or apply it in a language that supports it better.

Terms like coroutines, concurrency, promises, etc, can be confusing; I just like to demystify them with easy-to-grasp examples. That does mean that examples can be contrived or very simple, but they are designed to get the point across.

Thanks for all the comments so far!

Contrived examples are okay if they help trigger a click in the reader's mind, "wow, I could use this to solve problem X in an actual project!"

The difficulty with these examples is that they are very different from the actual tasks that everyday web developers would like to parallelize, such as long-running database queries and API requests. These things often take orders of magnitude longer than any pure-PHP loop that a typical webapp might contain.

An example that fires off an async query and yields the result when it's ready will probably produce the right click in the minds of many more people. (mysqli can do this, but the interface is convoluted and badly in need of a Promise-like wrapper. I'm not sure if PDO/PostgreSQL even supports async queries.)

I agree, but I had to draw the line somewhere on this article as it was already getting pretty long. And since I'm tackeling concurrency in the next post, it made more sense to me to start talking more about async there, with examples. Bear with me. Once that post is out, I'm updating this one which will reference the other for async examples. Thank you for your feedback!

Unfortunately, as HN has had more users, the quality of discussions has gone down a bit and is flooded with routine complaining of this kind.

You just discovered what happens when you talk about PHP, and there are similar "Godwin's laws" for other topics, such as IPv6 (we needed IPv4 with extra octets), Google/Apple/Microsoft (any company trying to achieve a commercial objective is always equivalent to "enshittification") etc. Don't mind these too much - it's a good article!

I've only read part of the article. So far, it's great.

I haven't used it in ages,but I like PHP...

Yes, there is! However, even if the `iterable` it was yielding from a different Generator, the "outer" generator would still be "running", which still makes it asymmetrical. `yield from` is mentioned in the other post on Generators, though.