How to include PHP files that require an absolute path?

I have a directory structure like the following;

script.php

inc/include1.php
inc/include2.php

objects/object1.php
objects/object2.php

soap/soap.php

Now, I use those objects in both script.php and /soap/soap.php, I could move them, but I want the directory structure like that for a specific reason. When executing script.php the include path is inc/include.php and when executing /soap/soap.php it's ../inc, absolute paths work, /mnt/webdev/[project name]/inc/include1.php... But it's an ugly solution if I ever want to move the directory to a different location.

So is there a way to use relative paths, or a way to programmatically generate the "/mnt/webdev/[project name]/"?

This should work

$root = realpath($_SERVER["DOCUMENT_ROOT"]);

include "$root/inc/include1.php";

Edit: added imporvement by aussieviking

You can use relative paths. Try __FILE__. This is a PHP constant which always returns the path/filename of the script it is in. So, in soap.php, you could do:

include dirname(__FILE__).'/../inc/include.php';

The full path and filename of the file. If used inside an include, the name of the included file is returned. Since PHP 4.0.2, __FILE__ always contains an absolute path with symlinks resolved whereas in older versions it contained relative path under some circumstances. (source)

Another solution would be to set an include path in your httpd.conf or an .htaccess file.

Another way to handle this that removes any need for includes at all is to use the autoload feature. Including everything your script needs "Just in Case" can impede performance. If your includes are all class or interface definitions, and you want to load them only when needed, you can overload the __autoload() function with your own code to find the appropriate class file and load it only when it's called. Here is the example from the manual:

function __autoload($class_name) {
    require_once $class_name . '.php';
}

$obj  = new MyClass1();
$obj2 = new MyClass2(); 

As long as you set your include_path variables accordingly, you never need to include a class file again.