PHP获取域名等URL地址

<?php
//获取域名或主机地址
echo $_SERVER['HTTP_HOST']."<br />";
//输出结果：www.w3h5.com 

//获取相对路径
echo $_SERVER['PHP_SELF']."<br />";
//输出结果：/PHP-URL.php

//获取网址参数
echo $_SERVER["QUERY_STRING"]."<br />";
//输出结果：num=123

//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 />";
//输出结果：http://www.w3h5.com/PHP-URL.php?num=123

echo 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'].'?'.$_SERVER['QUERY_STRING']."<br />";
//输出结果：http://www.w3h5.com/PHP-URL.php?num=123
 

//包含端口号的完整url
echo 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"]."<br />";
//输出结果：http://www.w3h5.com:80/PHP-URL.php?num=123

//只取路径
$url='http://'.$_SERVER['SERVER_NAME'].$_SERVER["REQUEST_URI"]."<br />";
echo dirname($url);
//输出结果：http://www.w3h5.com/PHP-URL.php?num=123
?>