php nested include behavior

Question

In many places in my code, I do things like:

file1.php:
<?php
include('../file2.php');

file2.php:
<?php
include('anotherdirectory/file3.php');

Depending on the server or settings I try this on, it either sets the relative paths from the "includer" or from the "includee". This is really confusing. So file1 might try to include "../anotherdirectory/file3.php" or it might try "anotherdirectory/file3.php".

What settings dictate this behavior? I want to have control over this...

Answer 1

I would recommend using absolute paths. A good way to do this while still being portable is to make a declaration like this in your public_html/index.php:

define('ROOT', dirname(__FILE__));

Then, you can write includes like this which are very easy:

include(ROOT.'/file.php');

Otherwise, PHP checks to see if the file is in the include path as defined by your php.ini. If it's not there, it tries a relative path to the current script. Which is unpredictable and unmaintainable since you may be nestingly including files from different relative locations.

Edit: If you're constantly including a lot of class files, you may want to look into autoloading. It makes everything way simpler if you're programming in an object-oriented style. I have personally never written the word 'include' in my code for a very long time.

Edit 2: You could use the php.ini directive auto_prepend_file to automatically include a one-line file with the definition of ROOT to each one of your scripts.

Answer 2

In cases when I need to use relative paths I use the following syntax:

include (realpath(dirname(__FILE__)."/another_folder/myfile.php");

Answer 3

With get_include_path() you can see, what the server configuration for this is. In most cases it looks like this:

.:/usr/lib/php

This means, the first place php is looking for a included file is the directory of the script that includes another. If it is not present there, php is looking in /usr/php/lib. If you add more paths, php will also look there for a matching file.

If you include a file, which includes another one, the "root" path is the path of the file which included another one at first.