$_SERVER['SERVER_NAME'] returns nginx reverse proxy port/name

Question

I am running WordPress under the following configuration:

Varnish (Port 80) -> nginx (Port 8080)

This is all working great except when some plugin or other tries to get my server name using $_SERVER['SERVER_NAME']. When that happens, it is getting back _:8080 as my server name and port. This is what the nginx config has:

server {
listen 8080;
server_name _;

What I need it to return is domain.com but if I change the nginx config, obviously, it stops listening on the port it needs to be (8080) (but changing the server_name works fine).

How can I have nginx listen on 8080 but have $_SERVER['SERVER_NAME'] return the correct port (or rather, not append the wrong port)?

Answer 1

_:8080 is the correct value for $_SERVER['SERVER_NAME'] in this configuration. It's explicitly defined to return the value of server_name. From the documentation:

The name of the server host under which the current script is executing. If the script is running on a virtual host, this will be the value defined for that virtual host.

It sounds like you are looking for $_SERVER['HTTP_HOST']. Note that you also need to have not configured Varnish to alter the Host: request header.

Answer 2

You can override the default value of $_SERVER['SERVER_NAME'] by adding a fastcgi_param directive after the include fastcgi_params; statement.

For example:

location ~ \.php$ {
    include fastcgi_params;
    fastcgi_param  SERVER_NAME  $http_host;
    ...
}

The value defined in the include file will be silently overwritten with the value of $http_host.