#测试网址:     http://localhost/blog/testurl.php?id=5
 
//获取域名或主机地址 
echo $_SERVER['HTTP_HOST'].""; #localhost
 
//获取网页地址 
echo $_SERVER['PHP_SELF'].""; #/blog/testurl.php
 
//获取网址参数 
echo $_SERVER["QUERY_STRING"].""; #id=5
 
//获取用户代理 
echo $_SERVER['HTTP_REFERER'].""; 
 
//获取完整的url
echo 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
echo 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'].'?'.$_SERVER['QUERY_STRING'];
#http://localhost/blog/testurl.php?id=5
 
//包含端口号的完整url
echo 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"]; 
#http://localhost:80/blog/testurl.php?id=5
 
//只取路径
$url='http://'.$_SERVER['SERVER_NAME'].$_SERVER["REQUEST_URI"]; 
echo dirname($url);
#http://localhost/blog

<?php 
  echo __FILE__ ; // 取得当前文件的绝对地址，结果：D:\www\test.php 
  echo dirname(__FILE__); // 取得当前文件所在的绝对目录，结果：D:\www\ 
  echo dirname(dirname(__FILE__)); //取得当前文件的上一层目录名，结果：D:\ 
?>