Built-in webserver not passing header correctly

[susnux]

Description

E.g. the ´Forwarded` header might appear more then once, NGinx and Apache correctly merge them into a comma separated list.
But the built-in server does not and just passes the first header set.

To test:

<?php
// index.php
var_dump($_SERVER['HTTP_FORWARDED']);

Run with:

php -S localhost:8000

Test with curl:

 curl -v -H 'Forwarded: for=127.0.0.1' -H 'Forwarded: for=unknown' localhost:8000
* Host localhost:8000 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:8000...
* Connected to localhost (::1) port 8000
* using HTTP/1.x
> GET / HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/8.10.1
> Accept: */*
> Forwarded: for=127.0.0.1
> Forwarded: for=unknown
> 
* Request completely sent off
< HTTP/1.1 200 OK
< Host: localhost:8000
< Date: Mon, 30 Sep 2024 17:28:59 GMT
< Connection: close
< X-Powered-By: PHP/8.3.11
< Content-type: text/html; charset=UTF-8
< 
string(13) "for=127.0.0.1"

Expected output:
for=127.0.0.1,for=unknown

PHP Version

8.3.11

Operating System

openSUSE Tumbleweek

[devnexen]

not familiar that much with cli but seems to me the callback to concat value to headers need to handle Forwarded based headers values differently to address it, will start to look at it later today.