Dynamically Loading Plugins

Hi all. I have need to dynamically load some classes. I have created an abstract class that defines a function. Note that I'm using PHP 4 so abstract is not enforced. 3rd party plugins will then implement this interface. Users will upload their plugins via a web interface. After I save the php class file to the directory ./plugins, I will need to load it later. Basically I need to do something like. $dir = dir("plugins"); while($entry=$dir->read() ) { //skip non class php files. if(!eregi(".+\.class\.php$", $entry )) { continue; }//end if //dynamically load class and call it //require class require_once("plugins/".$entry); //get the class name from the entry $classname = ??? ?; $plugin = new $classname(); //result array $results = $plugin->getObjects(); //do other stuff }//end while