Cache host in request

[lbassin]

Q	A
Branch?	4.4
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	#32709
License	MIT
Doc PR	-

This PR stores request's host in a private variable, so we don't have run the entire function again the second time you call $request->getHost()

[seriquynh]

Some tests are broken because $request doesn't change the host name when new HTTP_HOST or SERVER_NAME is set.

$request = new Request();
'' === $request->getHost(); // true
$request->initialize([], [], [], [], [], ['HTTP_HOST' => 'www.example.com']);
'' === $request->getHost(); // true
$request->initialize([], [], [], [], [], ['SERVER_NAME' => 'www.example.com']);
'' === $request->getHost(); // true

[seriquynh]

For the above example, we may clear the $host property while new server indexes are set or this is a breaking change, I think.

[fabpot]

@lbassin What's the status of this PR?

[nicolas-grekas]

I just had a look at the code: this cannot work because in order to reset the cached host, we'd need to track changes to headers and server variables. That's not possible.

I'd recommend getting the host once and reusing the return value instead.