Wordpress Multisite with nginx. Match subdirectories within location - wordpress

Question

I have multiple WordPress sites running in subdirectories.
Everything works great, but I'm looking to simplify my nginx configuration.
At the moment, when I add a location, I need to add an entry to my server {} configuration for the specified directory.
location / {
try_files $uri $uri/ /index.php?q=$args;
}
location /site1 {
try_files $uri $uri/ /site1/index.php?q=$args;
}
location /site2 {
try_files $uri $uri/ /site2/index.php?q=$args;
}
location /site2 {
try_files $uri $uri/ /site3/index.php?q=$args;
}
location /site4 {
try_files $uri $uri/ /site4/index.php?q=$args;
}
I tried adding a regex to match the subdirectory, but seem to have a problem with it.
location /([_-0-9a-zA-Z]/?) {
try_files $uri $uri/ /$1index.php?q=$args;
}
does not appear to do the trick. In theory that should match a subdirectory, or nothing, and be able to let me add new directories without having to touch the nginx configuration.
Any pointers would be appreciated.
#jedifans pointed out how to get the regex to work
Thanks. That did the trick on any pages, but when I go to / it just tries to download the index.php.
location ~ \.php$ {
try_files $uri =404;
fastcgi_split_path_info ^(.+\.php)(/.+)$;
include fastcgi_params;
fastcgi_pass php70;
fastcgi_keep_conn on;
}
location ~ ^/([_\-0-9a-zA-Z]*/?) {
try_files /$1$uri /$1$uri/ /$1index.php?q=$args;
}
However when I go to domain.com/site1/ i get a download of the index.php not the homepage. What's missing?

Answer 1

I think you are missing the following from your new location block, the ~ operator that says to nginx that it's a regular expression. Try:
location ~ ^/([_-0-9a-zA-Z]*/?) {
A few regex tweaks too, ^ to say it must begin with / and * to match more than one of those characters within [ and ]
Edit: after your question update, try the following try_files directive:
try_files $uri $uri/ /$1/index.php?q=$args;
$uri should work without the matched string prepended and I have added a / in between the matched query and the index.php;
Also make sure to have index index.php; at server{} level.