/** * Returns the day of the month for a date as a number between 1 and 31. * * The argument can be any expression as long as it resolves to a date. * * @see http://docs.mongodb.org/manual/reference/operator/aggregation/dayOfMonth/ * @see Expr::dayOfMonth * @param mixed|Expr $expression * @return self */ public function dayOfMonth($expression) { $this->expr->dayOfMonth($expression); return $this; }