nginx logged ip different than php $_SERVER['REMOTE_ADDR']

[xufengnju]

nginx/0.8.49
php in fastcgi mode, php version 5.3.5
pieces of nginx cofig file:

default log format:
 log_format  main  '$remote_addr - - [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent"';

 access_log  /app/logs/default.log  main;

        location ~ .*\.php$ {
            fastcgi_pass   127.0.0.1:9000;
            #fastcgi_pass  unix:/tmp/php-cgi.sock;
            fastcgi_index  index.php;
            fastcgi_param  SCRIPT_FILENAME   
/usr/local/www/default$fastcgi_script_name;
            include        /usr/local/nginx/conf/fastcgi_params;
        }

contents of fastcgi_params:


fastcgi_param  QUERY_STRING       $query_string;
fastcgi_param  REQUEST_METHOD     $request_method;
fastcgi_param  CONTENT_TYPE       $content_type;
fastcgi_param  CONTENT_LENGTH     $content_length;

fastcgi_param  SCRIPT_NAME        $fastcgi_script_name;
fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;
fastcgi_param  DOCUMENT_ROOT      $document_root;
fastcgi_param  SERVER_PROTOCOL    $server_protocol;

fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;

fastcgi_param  REMOTE_ADDR        $remote_addr;
fastcgi_param  REMOTE_PORT        $remote_port;
fastcgi_param  SERVER_ADDR        $server_addr;
fastcgi_param  SERVER_PORT        $server_port;
fastcgi_param  SERVER_NAME        $server_name;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fastcgi_param  REDIRECT_STATUS    200;

problem is:
I got this in my log:
124.95.xx.yy - - [01/Aug/2012:15:22:48 +0800] "GET
/ch111/index.php?111234 HTTP/1.0" 200 1483 "-" "Mozilla/4.0 (compatible;
MSIE 8.0; Windows NT 5.1; Trident/4.0)"
And I got $_SERVER['REMOTE_ADDR'] with a different ip when it is shown
on client's browser.
I am sure that the different ips are from the same client.

Before my web server, I have no balancers or other devices, but I am not
of the client's side.

Even if the client goes through some kind of proxy, no matter squid or
commercial ones, $_SERVER['REMOTE_ADDR']  should be always the same with
what is shown in nginx's log.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,229169,229169#msg-229169