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

//获取网页网址
echo $_SERVER['PHP_SELF']."<br>";

//获取网址参数
echo $_SERVER['QUERY_STRING']."<br>";

//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']."<br>";
echo 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'].'?'.$_SERVER['QUERY_STRING']."<br>";

//包含端口号的完整url
echo 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"]."<br>";

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