function registerErrorHandler($call_existing = true, $error_types = null)
    {
        if ($error_types !== null) {
            $this->error_types = $error_types;
        }
        $this->old_error_handler = set_error_handler(array($this, 'handleError'), E_ALL);
        $this->call_existing_error_handler = $call_existing;
        return $this;
    }