PHP Get virtual directory solution

PHP Get virtual directory
Daniel, please ask a question.
I am now a PHP site configured under IIS, and then built a uploadfile virtual directory under the site, how to get the real path of this virtual directory? For example, I want to upload files or to determine if there is a file in this directory Is_file ('/uploadfile/xxxxxxxxxxxxxxxxxx ') is always false, what is the easy way? Don't want to write configuration absolute path ~
------to solve the idea----------------------
You can build a PHP file in the directory that UploadFile points to, such as info.php

 
 Echo __dir__;

In the program that needs to get the uploadfile real path

$path = file_get_contents (' http://localhost/uploadfile/info.php ');

