PHP获取文件目录dirname(__FILE__),getcwd()

以discuz x2.5为例
D:/www/upload2.5/test.php
D:/www/upload2.5/source/class/class_test.php

test.php文件如下

<?php  
define('APPTYPEID', 2);  
define('CURSCRIPT', 'test');  
//by http://www.manongjc.com/article/1321.html
require './source/class/class_core.php';  

C::app()->init();  

echo DISCUZ_ROOT."<br/>";  

echo __FILE__."<br/>";  
echo dirname(__FILE__)."<br/>";  
$dir = getcwd();echo $dir;  

echo "<hr/>";  

include DISCUZ_ROOT."source/class/class_test.php";  
?>  

class_test.php文件如下

<?php  

echo __FILE__."<br/>";  
echo dirname(__FILE__)."<br/>";  
$dir2 = getcwd();echo $dir2;  
//by http://www.manongjc.com/article/1321.html
?>  

运行结果如下

D:\www\upload2.5\                             -->DISCUZ_ROOT
D:\www\upload2.5\test.php                     -->__FILE__
D:\www\upload2.5                              -->dirname(__FILE__)
D:\www\upload2.5                              -->getcwd()


D:\www\upload2.5\source\class\class_test.php  -->__FILE__
D:\www\upload2.5\source\class                 -->dirname(__FILE__)
D:\www\upload2.5                              -->getcwd()

由此可见
__FILE__代表所在文件的路径
getcwd()运行文件的所在目录


DISCUZ_X2.5根路径是这样创建的
所在文件D:\www\upload2.5\source\class\class_core.php

define('IN_DISCUZ', true);  
define('DISCUZ_ROOT', substr(dirname(__FILE__), 0, -12)); 

Magento根路径创建如下
根目录index.php中

define('MAGENTO_ROOT', getcwd());