HTTP 400

The plain HTTP request was sent to HTTPS port

能看到这篇文章说明你正尝试用ssl访问phpmyadmin,google一下早有牛人在07年就解决了这个问题:

fastcgi_pass  127.0.0.1:9000;
fastcgi_index index.php;
include fcgi.conf;
fastcgi_param HTTPS on;(加到这里,上下无所谓在大括号内即可)

加入

fastcgi_param HTTPS on;

平滑重启即可。