Oh, is it that hard to enable that setting in php.ini, or even
better, not to use it, but rather configure your Webserver to do
that?

it's not hard to let take care about compression in the webserver, but it doesn't make enough problems for some people when it's done based on request-headers so that it works without issues :-)

and hell: the webserver even can decide if brotli or gz compression satisfies the client, way too less troubles

> Oh, is it that hard to enable that setting in php.ini, 

It's not that hard.. but I think it could be simpler. 

> or even
> better, not to use it, but rather configure your Webserver to do
> that?

Is that better / recommended? Is that recommendation documented? ;)

> Is that better / recommended?

it was never the job of the scripting language to handle http compression

> Is that recommendation documented?

surely: https://httpd.apache.org/docs/2.4/mod/mod_deflate.html

> it was never the job of the scripting language to handle http compression

Sorry, I must've been doing it wrong for the past 20 years.

At https://www.php.net/manual/en/zlib.configuration.php I don't see anything about it being deprecated / not recommended.

yes, you did it wrong the past 20 years, i did that too 20 years ago but it only took me a year to realize that http compression only works proper if all request headers are taken into account on both sides and that it's idiotic trying to do that in the scripting language

why is it idiotic doing that in the scripting language? 

because its the webserver which is responsible for http and so common sense says the http-compression which is a part of that belongs there 

while you discuss on the wrong end we use brotli instead of gzip for modern clients over two years now