php require_once path confusion

Question

Hi,

I was writing an web app in php, when i encountered a strange situation. I wish to clear my confusion. To illustrate my problem, consider a web app of this structure:

/
    index.php
    f1/
        f1.php
    f2/
        f2.php

contents of these files:

index.php:

<?php require_once("f1/f1.php"); ?>

f1.php:

<?php require_once("../f2/f2.php"); ?>

f2.php: blank

now when I try to open index.php in my browser I get this error:

Warning: require_once(../f2/f2.php) [function.require-once]: 
failed to open stream: No such file or directory in /var/www/reqtest/f1/f1.php on line 2
Fatal error: require_once() [function.require]: 
Failed opening required '../f2/f2.php' (include_path='.:/usr/share/php:/usr/share/pear') in /var/www/reqtest/f1/f1.php on line 2

Is there something obvious I'm missing? how do include paths work in php?

---

Before I asked this question, I attempted to experiment and find out. I set up another test, like so:

/
    index.php
    f1/
        f1.php
        f2.php

index.php:

<?php require_once("f1/f1.php"); ?>

f1.php:

<?php require_once("f2.php"); ?>

f2.php: blank

To my surprise (and utter confusion), this worked out fine!

so what is the secret behind the path resolution?

Thanks

PS I saw this question, but it still does not answer the second case that i've stated here.

Answer 1

Normaly in you old structure

<?php require_once("f2/f2.php"); ?>

instead of

<?php require_once("../f2/f2.php"); ?>

should work. As far as i know php takes the paths from the initial script

Answer 2

When you open index.php, working dir is set to the folder this file resides in. And inside insluded f1.php this working dir does not change.

You can include files by using their absolute paths, relative to the current included file like this:

require_once(dirname(__FILE__).'/../../test/file.php')

But better consider using an autoloader if these files contain classes.

Answer 3

It sounds like your server has the open_basedir setting enabled in the PHP configuration. This makes it impossible to include (and open) files in folders above your in the directory structur (i.e., you can't use ../ to go up in the folder structure).

Answer 4

If you include another file, the working directory remains where the including file is.

Your examples are working as intended.

Edit: The second example works because . (actual directory) is in your include path (see your error message).

Edit2: In your second example, the key point of your interest is this line:

<?php require_once("f2.php"); ?>

At first it will look in the current working dir (/var/www/req_path_test), but does not find f2.php.

As fallback, it will try to find f2.php in your include_path ('.:/usr/share/php:/usr/share/pear'), starting with '.' (which is relative to the actual file, not the including one).

So './f2.php' works and the require does not fail.