获取网址和主机名

#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

//文件根目录

 $_SERVER['DOCUMENT_ROOT']