中文的注释是我自己翻译的  要是有错的地方 请指点下 小弟不胜感激

载了个bbpress  想学习下 一开始就遇到了这个问题

前两个判断 IIS版本还看的懂（网络上资料查的 或许是我理解错误）

到是到了第三个就看不懂了  请教下高手 这些代码的目的是做什么

感觉有点像ajax判断浏览器类型有几分相似之处

//如果$_SERVER['REQUEST_URI']内容为空 则运行
if ( empty( $_SERVER['REQUEST_URI'] ) ) {

 //判定是否是IIS7  并且赋值$_SERVER['REQUEST_URI']
 if (isset($_SERVER['HTTP_X_ORIGINAL_URL'])) {
  $_SERVER['REQUEST_URI'] = $_SERVER['HTTP_X_ORIGINAL_URL'];
 }
  //如果不是IIS7  判定是否是IIS6  并且赋值$_SERVER['REQUEST_URI']
 else if (isset($_SERVER['HTTP_X_REWRITE_URL'])) {
  $_SERVER['REQUEST_URI'] = $_SERVER['HTTP_X_REWRITE_URL'];
 }
 else
 {
  // 使用ORIG_PATH_INFO如果没有就使用PATH_INFO
  if ( !isset($_SERVER['PATH_INFO']) && isset($_SERVER['ORIG_PATH_INFO']) )
   $_SERVER['PATH_INFO'] = $_SERVER['ORIG_PATH_INFO'];

  // Some IIS + PHP configurations puts the script-name in the path-info (No need to append it twice)
  if ( isset($_SERVER['PATH_INFO']) ) {
   if ( $_SERVER['PATH_INFO'] == $_SERVER['SCRIPT_NAME'] )
    $_SERVER['REQUEST_URI'] = $_SERVER['PATH_INFO'];
   else
    $_SERVER['REQUEST_URI'] = $_SERVER['SCRIPT_NAME'] . $_SERVER['PATH_INFO'];
  }

  // Append the query string if it exists and isn't null
  if (isset($_SERVER['QUERY_STRING']) && !empty($_SERVER['QUERY_STRING'])) {
   $_SERVER['REQUEST_URI'] .= '?' . $_SERVER['QUERY_STRING'];
  }
 }
}