In PHP, you cannot include files in parent directories “../” from a file that has already been included from another file in a different directory. This has been a nuisance for a long time.

Here is a test case: (Files followed by their code)

/test1.php (This is the file that is called directly by the browser/apache)

<?
//This all works fine
print 'test1'_start;
require('foo/bar/test2.php');
print 'test1_end';
?>

/foo/bar/test2.php

<?
print 'test2_start';
require('blah/test3.php'); //This works fine because the include file it is in a subdirectory, not a parent directory of test2.php
require('../test4.php'); //This does not call fine (an error is thrown by php) because it is in a parent directory relative to test2.php, which was already included from the parent file (test1.php) in another directory (/). To fix this, use 'foo/test4.php'
print 'test2_end';
?>

/foo/bar/blah/test3.php
/foo/test4.php (This file is not reached by this example without the fixes mentioned in either the comment in test2.php, or below)
The obvious method to fix this whole conundrum is to always set all includes relative to one root path, and then make sure that path is always used with the set_include_path function if your parent file is not in the root directory. For example:
Another method would be to write a require/include wrapper that calculates paths from the current directory whenever a parent path “../” is used. Here is an example of this:

function _require($IncludeFile, $CurrentFile)
{
	$CurrentPath=preg_replace('/[^\/]+$/', '', $CurrentFile); //Remove the filename to get the current path
	require(realpath("$CurrentPath$IncludeFile"));
}

This method is called with 2 parameters: the relative path from the current include file to the file you want to include, and __FILE__
For example, line 4 of “/foo/bar/test2.php” above would now be:
The first line of the _require function could also be removed by using the __DIR__ constant (instead of __FILE__) which was added in PHP 5.3.0.