//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