root('wallabag_core'); $rootNode ->children() ->arrayNode('languages') ->prototype('scalar')->end() ->end() ->arrayNode('import') ->append($this->getAllowMimetypes()) ->end() ->end() ; return $treeBuilder; } private function getAllowMimetypes() { $node = new ArrayNodeDefinition('allow_mimetypes'); $node->prototype('scalar')->end(); return $node; } }