php - discuz的rewrite写法

Question

我这有四个路径

１　http://sun.disc/portal.php
２　http://sun.disc/forum.php
３　http://sun.disc/forum.php?mod=viewthread&tid=1&extra=page%3D1
４　http://sun.disc/forum.php?mod=guide

我希望访问第二个路径时跳转到第一个页面，而访问３，４时不受影响
请问这个nginx的rewrite怎么写呢？我写的都达不到效果
我完整的配置如下

server { 
    listen 80 ;#default_server;
    root /home/sun/workspace/disc/;
    index index.php  index.html index.htm index.nginx-debian.html;
    server_name sun.disc;
    location / {
        try_files $uri $uri/ =404;
   }
    location ~ \.php$ {
               fastcgi_buffer_size 128k;
               fastcgi_buffers 4 256k;
               fastcgi_busy_buffers_size 256k;
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/var/run/php5-fpm.sock;
    }

  location = /forum.php {
    if ( $args = ''   ) {
        rewrite ^ /portal.php;  
    }
  }
}

虽然实现了访问路径2时跳转到路径1,但是当访问路径3,4时仍然跳转到了路径1

Answer 1

写出来效果了，用到了一个参数$args

知识点
下面是完整的配置

server { 
    listen 80 ;#default_server;
    root /home/sun/workspace/disc/;
    index index.php  index.html index.htm index.nginx-debian.html;
    server_name sun.disc;
    location / {
        try_files $uri $uri/ =404;
   }
  location ~ \.php$ {
               fastcgi_buffer_size 128k;
               fastcgi_buffers 4 256k;
               fastcgi_busy_buffers_size 256k;
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/var/run/php5-fpm.sock;

  }
  if ($args = '') {
    rewrite forum.php /portal.php;
  }
}

注意if 那里要和括号有一个空格

Answer 2

也可以用$request_uri实现。但是不明白为什么location = /forum.php的时候，配置不生效呢？