How to combine array rows and make it variable - php

Question

I'm using this w3schools way to get data from the database:
$sql = "SELECT num_of_reservations FROM table WHERE date = '$date";
$result = $conn->query($sql);
while($row = $result->fetch_assoc()) {
echo $row["num_of_reservations"];
}
I have database which looks like this:
id - date - num_of_reservations - name
1 - 2017-02-02 - 3 - somebody
2 - 2017-02-02 - 5 - somebody
3 - 2017-02-02 - 7 - somebody
This works fine if I want to echo rows from the database, but now I need to make form which allows you to make reservation only if there is less than 15 reservations already at the same day. Problem in my current design is that every num_of_reservations row is going to different Array (because of while loop I quess) and I need to make them to + (3+5+7) so I can compare, is the num_of_reservations <=15 If it is I display ticket buying screen and if it's not I tell to pick another day.

Answer 1

You can use another query to get the sum of all reservations:
$sql = "SELECT SUM(num_of_reservations) AS sum_of_reservations FROM table WHERE date = '$date'";
$result = $conn->query($sql);
$row = $result->fetch_assoc();
if ($row['sum_of_reservations'] <= 15) {
//display ticket buying screen.
} else {
//tell to pick another day.
}