Added support for numeric header names

[nickdnk]

Hello

As discussed at Nyholm/psr7-server#35, here are some changes that seem to solve the problem.

This may be a premature PR, but it was the easiest way for me to demonstrate a cohesive solution with tests that works. @Zegnat did most of this, I just put it together.

[Zegnat]

Thank you for opening this PR and getting the ball rolling! I have left some comments.

The change requests for the extra trailing commas in the tests are a bit unnecessary maybe. We do not by default run php-cs-fixer on tests. But I see no reason not to try and stay consistent.

[Nyholm]

Thank you.

If this library (or the PSR specification) was PHP 7.2+. It would have a type hint for string on withAddedHeader. In fact, the PSR specify that the $header should be a string.

I dont think it is a good idea to convert an integer to a string. I think it is the callee (nyholm/psr7-server in this case) that should make sure it si giving a string to the withAddedHeader function.

[Nyholm]

Hm.. I see. So if we do ->withAddedHeader('0', 'foo'), we will convert that to an int because it is used as an array key.. hm.

EDIT: It is true for all ints https://3v4l.org/b3DRV

[Nyholm]

Im happy with this PR.

Sorry for my comment before. I had to read the full linked issue.

Please just add a comment.

[nickdnk]

Squashed.

[Zegnat]

Test passes and I couldn’t think of any more methods to test with it. So LGTM! 🚀

[nickdnk]

Hey guys

Can we merge this in and update the dev-dependencies of https://github.com/Nyholm/psr7-server/pull/36/files? The tests over there require this component to be updated as psr7-server uses it for tests which fail on that PR because of this.

[Nyholm]

Yes, This should be merged. Thank you

[nickdnk]

I just added another test of getHeader() and getHeaderLine() with a value of 0, just to future-proof this edge-case.

[nickdnk]

Hey guys

Can we get this released so we can complete Nyholm/psr7-server#36? I cannot fix the errors I get in my API without this, unless I switch to a different PSR7 implementation which I would like to avoid having to toy with at the moment.

@Nyholm @Zegnat