Switch from PHP-HTTP to PSR-18

[JaZo]

PHP-HTTP has been formalized into PSR-18 a while back. It would be really nice if we can switch to PSR-18 as this would allow us to use clients with 'native' PSR-18 support, but lacking PHP-HTTP support, such as Guzzle 7. Most (if not all) PHP-HTTP-clients also support PSR-18 so it should not be a big breaking change.

[jbelien]

Yes! You're absolutely right, that's definitely something we should do! 🎉

I'll try to find some time in the next few month to prepare that migration.

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I'm pretty sure @Nyholm could help on that topic :P

[Nyholm]

We just need to drop php5. We can even do thin without breaking BC if I remember correctly.

[holtkamp]

For people who would like to understand this request, some additional documentation can be found here: http://docs.php-http.org/en/latest/httplug/introduction.html#client-interfaces

[jbelien]

@JaZo Would you have time to submit a PR ? Thanks :)

[JaZo]

I'd love to get this through, but don't exactly know how to do it without breaking BC. @Nyholm do you have some guidance or examples to get this through without breaking BC?

[Nyholm]

If we dont use any async stuff. Then there is no real BC break, Of course it is a technical BC break and we should update the major version. But befeore we are ready for a new major release, we can use both PSR18 and HTTPlug at the same time.

[JaZo]

Okay, I'll give it a go!