/** * Builds a single string for the given scope columns values. Useful for * making array keys for grouping. * * @param Tree\Node $node * @return string */ protected function keyForScope($node) { return implode('-', array_map(function ($column) use($node) { $value = $node->getAttribute($column); if (is_null($value)) { return 'NULL'; } return $value; }, $node->getScopedColumns())); }