//获取域名或主机地址
echo $_SERVER['HTTP_HOST']."<br />"; #afish.cnblogs.com

//获取网页地址
echo $_SERVER['PHP_SELF']."<br />"; #/p/3941211.html

//获取网址参数
echo $_SERVER["QUERY_STRING"]."<br />"; #id=1

//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://afish.cnblogs.com/p/3941211.html?id=1

//包含端口号的完整url
echo 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"];
#http://afish.cnblogs.com:80/p/3941211.html?id=1

//只取路径
$url='http://'.$_SERVER['SERVER_NAME'].$_SERVER["REQUEST_URI"];
echo dirname($url);
#http://afish.cnblogs.com/p

top.location.href   顶级窗口的地址
this.location.href  当前窗口的地址