public function renderToggle(array $aDropdownOptions)
    {
        // Dropdown toggle
        if (empty($aDropdownOptions['label'])) {
            $aDropdownOptions['label'] = '';
        } elseif (!is_scalar($aDropdownOptions['label'])) {
            throw new InvalidArgumentException('"label" option expects a scalar value, "' . gettype($aDropdownOptions['label']) . '" given');
        } elseif (($oTranslator = $this->getTranslator())) {
            $aDropdownOptions['label'] = $oTranslator->translate($aDropdownOptions['label'], $this->getTranslatorTextDomain());
        }

        // Dropdown toggle attributes (class)
        if (empty($aDropdownOptions['toggle_attributes'])) {
            $aDropdownOptions['toggle_attributes'] = array('class' => 'sr-only dropdown-toggle');
        } else {
            if (!is_array($aDropdownOptions['toggle_attributes'])) {
                throw new InvalidArgumentException('"toggle_attributes" option expects an array, "' . gettype($aDropdownOptions['toggle_attributes']) . '" given');
            }

            if (empty($aDropdownOptions['toggle_attributes']['class'])) {
                $aDropdownOptions['toggle_attributes']['class'] = 'sr-only dropdown-toggle';
            } else {
                if (!preg_match('/(\s|^)sr-only(\s|$)/', $aDropdownOptions['toggle_attributes']['class'])) {
                    $aDropdownOptions['toggle_attributes']['class'] .= ' sr-only';
                }
                if (!preg_match('/(\s|^)dropdown-toggle(\s|$)/', $aDropdownOptions['toggle_attributes']['class'])) {
                    $aDropdownOptions['toggle_attributes']['class'] .= ' dropdown-toggle';
                }
            }
        }

        // Dropdown toggle attributes (data-toggle)
        if (empty($aDropdownOptions['toggle_attributes']['data-toggle'])) {
            $aDropdownOptions['toggle_attributes']['data-toggle'] = 'dropdown';
        }

        // Dropdown toggle attributes (role)
        if (empty($aDropdownOptions['toggle_attributes']['role'])) {
            $aDropdownOptions['toggle_attributes']['role'] = 'button';
        }

        // Dropdown toggle attributes (href)
        if (empty($aDropdownOptions['toggle_attributes']['href'])) {
            $aDropdownOptions['toggle_attributes']['href'] = '#';
        }

        // Dropdown toggle attributes (id)
        if (!empty($aDropdownOptions['name'])) {
            $aDropdownOptions['toggle_attributes']['id'] = $aDropdownOptions['name'];
        }

        $aValidTagAttributes = $this->validTagAttributes;
        $this->validTagAttributes = array('href' => true);
        $sAttributeString = $this->createAttributesString($aDropdownOptions['toggle_attributes']);
        $this->validTagAttributes = $aValidTagAttributes;

        return sprintf(
                static::$dropdownToggleFormat, $sAttributeString, // Toggle attributes
                $this->getEscapeHtmlHelper()->__invoke($aDropdownOptions['label']) // Toggle label
        );
    }