Nginx rewrite rule for codeigniter for URL parameters - php

Question

I did the following configurations for nginx server for code igniter and worked correctly , unfortunately there is one case not working.
When I request URL with parameter Like
servername.com/ControllerName/methodName?param=value
I got Not found Page 404
Server Configurations :
server {
# access from localhost only
listen 127.0.0.1:80;
server_name serverName.com;
root API;
log_not_found off;
charset utf-8;
access_log logs/accessservername.log main;
index index.php;
# handle files in the root path /www
location / {
try_files $uri $uri/ /index.php?$args;
}
#error_page 404 /404.html;
# redirect server error pages to the static page /50x.html
#
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root API;
}
# pass the PHP scripts to FastCGI server listening on 127.0.0.1:9100
#
location ~ \.php$ {
try_files $uri =404;
fastcgi_pass php;
fastcgi_index index.php;
#fastcgi_param PHP_FCGI_MAX_REQUESTS 1000;
#fastcgi_param PHP_FCGI_CHILDREN 100;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param REMOTE_ADDR $http_x_real_ip;
include fastcgi_params;
}
# add expire headers and speed up image access with a vary header
location ~* ^.+.(gif|ico|jpg|jpeg|png|flv|swf|pdf|mp3|mp4|xml|txt|js|css)$ {
expires 30d;
add_header Vary Accept-Encoding;
}
# only allow these request methods
if ($request_method !~ ^(GET|HEAD|POST)$ ){ return 405; }
}