//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://www.111cn.net /blog/testurl.php?id=5

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

<?php
// 说明：获取完整url

function curpageurl()
{
    $pageurl = 'http';

    if ($_server["https"] == "on")
    {
        $pageurl .= "s";
    }
    $pageurl .= "://";

    if ($_server["server_port"] != "80")
    {
        $pageurl .= $_server["server_name"] . ":" . $_server["server_port"] . $_server["request_uri"];
    }
    else
    {
        $pageurl .= $_server["server_name"] . $_server["request_uri"];
    }
    return $pageurl;
}
?>