@shizobuddy: /path/to/php is usually $document_root if set properly so you come
up with the following generic config:

fastcgi_param SCRIPT_FILENAME $document_root/$fastcgi_script_name;

@androo: instead of setting fastcgi_param in a if (in fact you can't), you can
still set variables to do so. Example

set $script index.php; set $path_info ""; if ($uri ~ "^(.+\.php)(.*)") { set $script $1; set $path_info $2; } fastcgi_param PATH_INFO $path_info; ....

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,866,30886#msg-30886