Nginx problems

I just try to use nginx with virtualmin. but my website always get 502 bad gateway error.
So, I look into log

PHP Notice: Undefined index: error in /home/example/public_html/validate.php on line 95" while reading response header from upstream, client: xxx.xxx.xxx.xxx, server: example.com, request: "POST /validate.php HTTP/1.1", upstream: "fastcgi://unix:/var/php-nginx/13981527782438.sock/socket:", host: "example.com", referrer: "http://example.com/" 2014/04/26 07:15:42 [error] 5275#0: *108275 FastCGI sent in stderr: "PHP Notice: Undefined index: opt in /home/example/public_html/validate.php on line 214" while reading response header from upstream, client: xxx.xxx.xxx.xxx, server: example.com, request: "POST /validate.php HTTP/1.1", upstream: "fastcgi://unix:/var/php-nginx/13981527782438.sock/socket:", host: "example.com", referrer: "http://example.com/"

example.com replace my domain and xxx.xxx.xxx.xxx replace my ip.

What I had to do is, start the service

service php-fcgi-example-com start

and my site will be online as usual.

Why I need to run php-fcgi-gm-likerz-us manually? is it die or something??