/** * Compares two values and returns: * -1 if the first value is less than the second. * 1 if the first value is greater than the second. * 0 if the two values are equivalent. * * @see http://docs.mongodb.org/manual/reference/operator/aggregation/cmp/ * @see Expr::cmp * @param mixed|Expr $expression1 * @param mixed|Expr $expression2 * @return self */ public function cmp($expression1, $expression2) { $this->expr->cmp($expression1, $expression2); return $this; }