/** * Returns the hour portion of a date as a number between 0 and 23. * * The argument can be any expression as long as it resolves to a date. * * @see http://docs.mongodb.org/manual/reference/operator/aggregation/hour/ * @see Expr::hour * @param mixed|Expr $expression * @return self */ public function hour($expression) { $this->expr->hour($expression); return $this; }