访问PHP文件File not found错误原因

server {
listen [::]:80;
server_name example.com www.example.com;
access_log /var/www/logs/example.com.access.log;

location ~ .php$ {
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME /var/www/example.com$fastcgi_script_name;
include fastcgi_params;
}

}
此配置有两处错误：
1）不应该把SCRIPT_FILENAME写死，应该写成$document_root
2）在server下应该增加root的配置，否则在访问php文件的时候会报File not found