Php mariadb sum divided by if there is no value, can NAN, be shown as 0?

$selectTip = $pdo->query("SELECT * FROM `tips_rate`
                WHERE `tip_id` = "".$row["id"]."" "
              );
              $selecttotal = mysqli_num_rows($selectTip);
              $rate = $pdo->query("SELECT SUM(star) as startotal FROM `tips_rate`
                WHERE `tip_id` = "".$row["id"]."" "
              );
              $startotal = mysqli_fetch_array($rate);
              echo $startotal["startotal"]/$selecttotal;

when we echo the result of their division by
there is no value, he will see NAN.. Can you show me 0?

Mysqli mariadb php

Feb.26,2021

$num = $startotal ['startotal'] / $selecttotal;
echo is_nan ($num)? 0: $num;

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