NGINX Ajax - PHP 404错误

I have written a simple AJAX function which communicates with a PHP web Service. It works fine in local (IIS + PHP) , but in production environment an AJAX call to the PHP file throws a 404 error (Not Found)

This seems to be an NGNX config issue , so pasting the relevant NGINX config

server {
        listen       80 default_server;
        listen       [::]:80 default_server;
        server_name  _;
        root         /usr/share/nginx/html;

        # Load configuration files for the default server block.
        include /etc/nginx/default.d/*.conf;

        location / {
        }

        error_page 404 /404.html;
            location = /40x.html {
        }

        error_page 500 502 503 504 /50x.html;
            location = /50x.html {
        }

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000

    location ~ \.php$ {
        root           /usr/share/nginx/html;
        fastcgi_pass   127.0.0.1:9000;
        fastcgi_index  index.php;
        fastcgi_param  SCRIPT_FILENAME   $document_root$fastcgi_script_name;
        include        fastcgi_params;
    }   

Please suggest a work around.