include path

What dirname() will return can be discerned via these pages.
http://php.net/manual/en/function.dirname.php
http://php.net/manual/en/language.constants.predefined.php

In the case with __FILE__, php says, "The full path and filename of the file with symlinks resolved. If used inside an include, the name of the included file is returned."

You can (at least) do one of the follwoing:
1) add your library directory to "include_path" directive in php.ini, or
2) without access to php.ini, use relative path in your code, for example, something like: include("../../../library/config.php");

but the thing is there will be multiple config files, one in each project folder, each with the connection string for the database for that project.
           
There is a  file is located in mySite.com/DataTables/Editor/php/Bootstrap.php, outside of any of the project folders, so that I don't have to copy all the DataTables files into each project folder.  Each project will have it's own page that has the statement:
      include( "../../DataTables/Editor/php/DataTables.php" );

This DataTables.php is the one with the statement:  include( dirname(__FILE__).'/config.php' );

So I need DataTables.php to know that it is being included from mySite.com/Project1/ or mySite.com/Project2/, etc.

So I guess, long story short:  how to the path of the file that called it?

just thought of another way to clarify (I hope)

www.mySite.com/Project1/lib/config.php (contains connection info for database that Project1 uses)
www.mySite.com/Project1/lib/getMathFacts.php

www.mySite.com/Project2/lib/config.php (contains connection info for a different database that Project2 uses)
www.mySite.com/Project2/lib/getStateCapitols.php

each of the "get" php files has the same line:
      include( "../../DataTables/Editor/php/DataTables.php" );

www.mySite.com/DataTables/Editor/php/DataTables.php needs to include the config file.
        So if it was called from Project1 it includes www.mySite.com/Project1/lib/config.php.  
        If it is called from Project2 it includes www.mySite.com/Project2/lib/config.php

oh my goodness.  I can't believe I didn't think of this...

right before I have my include DataTables I set a variable:
   $myPath = dirname(__FILE__), which would get the path of the current project

Then, in DataTables I use this in the include:
   include( $myPath.'/config.php' );