public function message_count($msg_type = '', $reverse = false) {
        /*
        **  returns the number of messages in the queue
        **  if $msg_type is defined, it returns the number of messages of the class $msg_type
        */
        
        if (empty($msg_type)) {
            return count($this->messages);
        } else {
            $msg_count = 0;
            
            foreach($this->messages as $msg) {
                if (strtolower($msg_type) == strtolower(get_class($msg)) && !$reverse) {
                    $msg_count++;
                }

                if (strtolower($msg_type) != strtolower(get_class($msg)) && $reverse) {
                    $msg_count++;
                }
            }
            
            return $msg_count;
        }
    }