/** * Returns the value that results from applying an expression to the last * document in a group of documents that share the same group by a field. * Only meaningful when documents are in a defined order. * * @see http://docs.mongodb.org/manual/reference/operator/aggregation/last/ * @see Expr::last * @param mixed|Expr $expression * @return Operator */ public function last($expression) { $this->expr->last($expression); return $this; }