php - Reading from file (require) -

i have this: http://i.imgur.com/kpulybg.png , im working on "admin" folder , inside of have "admin.php", problem want read "core/init.php" there. have in admin.php

<?php require '../includes/header.php'; ?>  <?php $user = new user(); if(!$user->isloggedin()){     redirect::to(404); } else if(!$user->haspermission('admin')){     redirect::to(404); } ?> <div id="content">  </div>  <?php require '../includes/footer.php'; ?> 

and inside "includes/header.php" have php require_once 'core/init.php'; admin page:

warning: require(core/init.php): failed open stream: no such file or directory in c:\xampp\htdocs\oop\includes\header.php on line 2  fatal error: require(): failed opening required 'core/init.php' (include_path='.;c:\xampp\php\pear') in c:\xampp\htdocs\oop\includes\header.php on line 2 

i know have add ../ error on index.php page must run without because not inside folder, runs header , footer includes folder.

as documentation explains:

files included based on file path given or, if none given, include_path specified.

...

if path defined — whether absolute (starting drive letter or \ on windows, or / on unix/linux systems) or relative current directory (starting . or ..) — include_path ignored altogether.

how applies code?

require_once 'core/init.php'; - php searches paths php.ini directive include_path. appends core/init.php each path list , checks if path computed way exists. doesn't.

require_once './core/init.php'; - include_path doesn't matter; provided relative path (core/init.php) appended current directory path of file;

what's solution?

none of above ways works in practice.

the safest method include files using subdirectories use magic constant __dir__ , function dirname() compute correct file path.

require '../includes/header.php'; 

becomes

require dirname(__dir__).'/includes/header.php'; 

and

require_once 'core/init.php'; 

becomes

require_once dirname(__dir__).'/core/init.php'; 

because __dir__ directory current file (includes/header.php) located.