配置目的： 一个子目录下的代码使用框架，其他部分不采用。
配置如下（仅server段，其他参见nginx文档）：

        server {

                listen   80;
                server_name localhost.dev;
                index index.php index.html index.htm i.php;
                set $root_path '/var/www/';
                root $root_path;

                client_max_body_size 2M;

                location /backend {
                    # if (-f $request_filename) { break; }
                    rewrite ^/backend/(.*)$ /backend/public/index.php?_url=/$1;
                }

                location ~ \.php {
                fastcgi_buffer_size 128k;
                fastcgi_buffers 4 256k;
                fastcgi_busy_buffers_size 256k;
                        fastcgi_pass   127.0.0.1:9000;
                        fastcgi_index  /index.php;

                        include fastcgi_params;

                        fastcgi_split_path_info       ^(.+\.php)(/.+)$;
                        fastcgi_param PATH_INFO       $fastcgi_path_info;
                        fastcgi_param PATH_TRANSLATED $document_root$fastcgi_path_info;
                        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
                }

                location ~* ^/(css|img|js|flv|swf|download)/(.+)$ {
                        root $root_path;
                }

                location ~ /\.ht {
                        deny all;
                }
        }