Braintree\Util::_flattenArray PHP Method

    private static function _flattenArray($keys, $namespace = null)
    {
        $flattenedArray = [];
        foreach ($keys as $key) {
            if (is_array($key)) {
                $theKeys = array_keys($key);
                $theValues = array_values($key);
                $scope = $theKeys[0];
                $fullKey = empty($namespace) ? $scope : $namespace . '[' . $scope . ']';
                $flattenedArray = array_merge($flattenedArray, self::_flattenArray($theValues[0], $fullKey));
            } else {
                $fullKey = empty($namespace) ? $key : $namespace . '[' . $key . ']';
                $flattenedArray[] = $fullKey;
            }
        }
        sort($flattenedArray);
        return $flattenedArray;
    }