Getting wrong $_SERVER[‘SERVER_NAME’] on Nginx PHP5-FPM

I was testing some old code that used $_SERVER[‘SERVER_NAME’] to get the sub domain, but I was getting *.mysite.com  no matter what was the sub domain, so looking on the nginx site config file on the php section had and include

location ~ \.php$ {
fastcgi_split_path_info ^(.+\.php)(/.+)$;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
include fastcgi_params; #<-- includes fastcgi paramters file
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_intercept_errors off;
fastcgi_buffer_size 16k;
fastcgi_buffers 4 16k;
}

which calls a file /etc/nginx/fastcgi_params

On the file I found the problem, nginx send as SERVER_NAME parameter the $server_name var, which in this case because we use wildcards  anysubdomain.mysite.com will trigger *.mysite.com  and that’s why the nginx variable get $server_name get that domain

To fix this problem I just comment that $server_name and use the $http_host variable.

fastcgi_param  SERVER_NAME        $http_host; #$server_name;

Restart nginx and test

sudo service nginx restart