X-Forwarded-Host header is not working when an array or comma separated list is used

[benoitf]

Headers can be array values or be a single string with comma separated value

So when computing the host using X-Forwarded-Host it should use the first value and not the 'joined' list concatenate by a comma else it leads to invalid base URL

example:

https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#x-headers

Be careful when using these headers on the origin server, since they will contain more than one (comma-separated) value if the original request already contained one of these headers. For example, you can use %{X-Forwarded-For}i in the log format string of the origin server to log the original clients IP address, but you may get more than one address if the request passes through several proxies.