#测试网址:     http://localhost/blog/testurl.php?id=5  
      
    //获取域名或主机地址   
    echo $_SERVER['HTTP_HOST']."<br>"; #localhost  
      
    //获取网页地址   
    echo $_SERVER['PHP_SELF']."<br>"; #/blog/testurl.php  
      
    //获取网址参数   
    echo $_SERVER["QUERY_STRING"]."<br>"; #id=5  
      
    //获取用户代理   
    echo $_SERVER['HTTP_REFERER']."<br>";   
      
    //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