Exploring Coroutines in PHP

I think neither does PHP have the ecosystem for it, nor does it have the language primitives or standard library for it. Much cleaner languages than PHP already have enough issues getting concurrency things like fibers right. I don't see this ending in any implementation, that doesn't have surprising dysfunctional parts in it. Especially not, when again and again people behind PHP chose the easy way out for adding language features, like they did with lambdas, that don't capture their environment, unless you explicitly state what they capture.

Let alone the standard library being an unfixable mess, if they want to pursue backwards compatibility. What they would need to do is a clean break. Something like "PHP 10 is a breaking change, we are modernizing the base language and standard library and getting rid of decades of cruft." -- Which then many PHP users would hate.

No, PHP is a not a language whose design has what it takes. A library that claims to have such advanced stuff implemented in PHP is not to be easily trusted to be free of hassle and tripwire, because the language itself has those built-in. For example with Fibers, one has to manually call suspend and resume. Other languages get fibers done without this hassle.

EDIT: For all the downvoters, who don't care to actually give reasons or discuss, the cracks are already showing in the Fibers manual itself. Look at the first comment for example: https://www.php.net/manual/en/language.fibers.php#127282 which links to a bug/issue in the Fibers repo. It is a bug, even recognized via issue label, it is verified, as recognized via issue label, and it is ... closed. Apparently it will not be fixed, and has been simply closed.