Nginx加载索引文件时遇到问题

我有这个nginx vhost文件

server { # php/fastcgi
    listen       80;
    server_name  trinityplex.com www.trinity.com;
    access_log   /home/web/trinity_web/log/access.log;
    root /home/web/trinity_web/public;
    location / {
      index    index.html index.htm index.php;
    }
}

(域trinityplex.com)，但如果我去trinityplex.com nginx显示我502坏网关和抛出索引文件- chrome下载index.php像一个正常的下载

太可笑了，我从来没见过那个。如果我问PHP版本它会转储

PHP 5.3.5-0.dotdeb.0 with Suhosin-Patch (cli) (built: Jan  7 2011 00:30:52) 
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies
    with Suhosin v0.9.32.1, Copyright (c) 2007-2010, by SektionEins GmbH

你有什么办法解决这个问题吗?

这是一个nginx配置文件

user root;
worker_processes  1;
events {
    worker_connections  1024;
}
http {
    include       mime.types;
    default_type  application/octet-stream;
    sendfile        on;
    keepalive_timeout  65;
    server_names_hash_bucket_size 128;
    gzip  on;
    include /usr/local/nginx/sites-enabled/*;
}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        location ~ .php$ {
                fastcgi_pass   127.0.0.1:9000;
                fastcgi_param  SCRIPT_FILENAME $document_root$fastcgi_script_name;
                fastcgi_index  index.php;
                include        fastcgi_params;
        }