public function on(string $event, $class_or_obj, string $method, array $arguments = []): Core
    {
        $this->registerEventHandler(new EventHandler($event, $class_or_obj, $method, $arguments));
        return $this;
    }
public function on(string $event, $class_or_obj, string $method, array $arguments = []): Core
    {
        $this->registerEventHandler(new EventHandler($event, $class_or_obj, $method, $arguments));
        return $this;
    }
public function on ( string $ event , $ class_or_obj , string $ method , array $ arguments = [ ] ) : Core { $ this -> registerEventHandler ( new EventHandler ( $ event , $ class_or_obj , $ method , $ arguments ) ) ; return $ this ; }
Create an event handler to be called when a specified event is fired by the framework or a library within the
Framework.

@param string $event        The name of the event to listen for
@param mixed  $class_or_obj The object or class the method belongs to
@param string $method       The method to call
@param array  $arguments    Optional parameters to pass to the method

@return Core
@throws \Exception
Create an event handler to be called when a specified event is fired by the framework or a library within the Framework .