Nginx client_max_body_size per location block (with php frontcontroller pattern)

If /admin/upload path is virtual, it is possible to make it work as follows:

location / {
    try_files $uri /index.php?$args;
}

location /admin/upload {
    client_max_body_size 256M;

    include inc/php.conf;
    rewrite ^(.*)$ /index.php?$args break;
}

location ~ \.php$ {
    include inc/php.conf;
}

Not the prettiest too, but works.

Define two php locations?

location ~ ^/admin/upload/.+\.php$
{
    client_max_body_size 256M;
    include /etc/nginx/conf.d/php-fpm.conf;
}   
location ~ \.php
{
    include /etc/nginx/conf.d/php-fpm.conf;
}

Perhaps not the prettiest... Should be functional though..

Using multiple locations is possible, but is a bit tricky.

If you use try_files or rewrite as explained above, then the client_max_body_size would be set to the client_max_body_size of the higher context, not really the one for the location block you'd expect it to.

Move your PHP FastCGI configuration into a file that you can include, such as php-conf.conf.

Then use such a configuration:

    location / {
        # try to serve file directly, fallback to index.php
        try_files $uri /index.php$query_string;
    }

    location ~ ^/admin/upload$ {
        client_max_body_size 4m;
        include /etc/nginx/php-conf.conf;
        fastcgi_param SCRIPT_FILENAME $realpath_root/index.php;
    }

    location ~ ^/index\.php(/|$) {
        include /etc/nginx/php-conf.conf;
        internal;
    }

Note that you need to overwrite SCRIPT_FILENAME to use index.php if you have a different script name set. This could happen because of fastcgi_split_path_info ^(.+\.php)(/.*)$;.