create libraries using existing multiple classes

[eluser]tirso[/eluser]
hi to all

I have downloaded working phptreegraph, I want to used it using codeigniter framework. This class to work composed three classes (gdrenderer.ph,tree.php and node.php). I have already created some class but very simple. In this case, do i have to re-write it in one class or there is a better way to load it in my view just loading the main class gdrenderer.php? I tried to copy all these three classes in my application/libaries and in my view I called main class GDRenderer.php like below

Code:

include_once(APPPATH.'/libraries/GDRenderer.php');    
$objTree = new GDRenderer(30, 10, 30, 50, 20);

inside GDRenderer.php (upper part) I called Tree.php like below

Code:

include_once(APPPATH.'/libraries/Tree.php');

inside Tree.php (upper part) I called Node.php like below

Code:

include_once(APPPATH.'/libraries/Node.php');

the error
The image “http://localhost/codeigtest/index.php/phptreegraph” cannot be displayed, because it contains errors.