PHP path - including a file from the same directory

I have a problem with my path. Say I have a PHP file in /home/bla/www/dev/source/test.php. In this test.php file I want to include a file in

/home/bla/www/config/conf.php

<?php
    include_开发者_如何学Pythononce("");
?>

I don't want to include it like include /home/bla/www/config/conf.php. How can I do it?

PS: This fails:

include_once("../../config/conf.php");

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I'd suggest to use an absolute path instead of a relative:

include_once($_SERVER['DOCUMENT_ROOT']."/config/conf.php"); 

This would work from any folder.

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$current_dir = dirname(__FILE__);
require_once($current_dir.'/../foo/bar.php');

Note that require_once('foo.php') looks for foo.php in the same directory as the script, but require_once('../foo.php') is not relative to the path of the script, but relative to the current working directory.

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As DaDaDom suggests, permissions may well be the problem here. Have you tried addressing the file using an absolute path (/home/bla/www/config/conf.php), and if it fails, what's the error?