我觉得这个方法不错，试试吧

if($_SERVER['HTTP_HOST'] == "localhost"){
    define('SITEURL', 'http://' . $_SERVER['HTTP_HOST']);
    define('SITEPATH', $_SERVER['DOCUMENT_ROOT']);
    define('CSS', $_SERVER['DOCUMENT_ROOT'] . '/css/');
    define('IMAGES', $_SERVER['DOCUMENT_ROOT'] . '/images/');
}
else{
    define('SITEURL', 'http://' . $_SERVER['HTTP_HOST']);
    define('SITEPATH', $_SERVER['DOCUMENT_ROOT']);
    define('TEMPLATE', $_SERVER['DOCUMENT_ROOT'] . '/incs/template/');
    define('CSS', $_SERVER['DOCUMENT_ROOT'] . '/css/');
    define('IMAGES', $_SERVER['DOCUMENT_ROOT'] . '/images/');
}

看一下$_SERVER['REQUEST_URI']，即

$actual_link = "http://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";

(注意双引号字符串语法是完全正确的)

如果你想同时支持HTTP和HTTPS，你可以使用

$actual_link = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http") . "://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";

编者注:使用此代码具有安全隐患。客户端可以将HTTP_HOST和REQUEST_URI设置为它想要的任意值。

Use:

$base_dir = __DIR__; // Absolute path to your installation, ex: /var/www/mywebsite
$doc_root = preg_replace("!{$_SERVER['SCRIPT_NAME']}$!", '', $_SERVER['SCRIPT_FILENAME']); # ex: /var/www
$base_url = preg_replace("!^{$doc_root}!", '', $base_dir); # ex: '' or '/mywebsite'
$base_url = str_replace('\\', '/', $base_url);//On Windows
$base_url = str_replace($doc_root, '', $base_url);//On Windows
$protocol = empty($_SERVER['HTTPS']) ? 'http' : 'https';
$port = $_SERVER['SERVER_PORT'];
$disp_port = ($protocol == 'http' && $port == 80 || $protocol == 'https' && $port == 443) ? '' : ":$port";
$domain = $_SERVER['SERVER_NAME'];
$full_url = "$protocol://{$domain}{$disp_port}{$base_url}"; # Ex: 'http://example.com', 'https://example.com/mywebsite', etc. 

来源:PHP文档根，路径和URL检测

我用了这句话。

$base = "http://$_SERVER[SERVER_NAME]:$_SERVER[SERVER_PORT]$my_web_base_path";
$url = $base . "/" . dirname(dirname(__FILE__));

我用这个函数来处理URL:

 <?php
     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;
     }
 ?>

非常简单的用法:

function current_url() {
    $current_url  = ( $_SERVER["HTTPS"] != 'on' ) ? 'http://'.$_SERVER["SERVER_NAME"] :  'https://'.$_SERVER["SERVER_NAME"];
    $current_url .= ( $_SERVER["SERVER_PORT"] != 80 ) ? ":".$_SERVER["SERVER_PORT"] : "";
    $current_url .= $_SERVER["REQUEST_URI"];

    return $current_url;
}