Processing SQL query result in PHP, then inserting again within same function

Question

I'm trying to make a function work, where I ask for a number of free seats left in a car, and if executed, it subtracts 1 from the result and updates the cell in database.

Sql statements must be correct... am I missing out on anything else?

function seatCalc($id){

    $stmt=$this->connection->prepare("SELECT seats_left FROM drive WHERE id=?");
    $stmt->bind_param("i", $id);
    $stmt->bind_result($seat_count);
    $stmt->execute();

    return $seat_count;

    if($seat_count >= 1){

        $seat_count -= 1;

        $stmt=$this->connection->prepare("UPDATE drive SET seats_left=? WHERE id=?");
        $stmt->bind_param("ii", $seat_count, $id);
        $stmt->execute();
    }

}

It's a part of my university project and unfortunately, I can't reach my professor at the moment.

Thank you in advance!

Answer 1

您的return语句会在处理if块之前使您脱离函数。

Answer 2

• your condition is incorrect;
• you have unreached statements after return;

Here is code:

function seatCalc($id){
  $stmt=$this->connection->prepare("SELECT seats_left FROM drive WHERE id=?");
  $stmt->bind_param("i", $id);
  $stmt->bind_result($seat_count);
  $stmt->execute();
  if($seat_count > 0){
    $stmt=$this->connection->prepare("UPDATE drive SET seats_left=seats_left-1 WHERE id=?");
    $stmt->bind_param("i", $id);
    $stmt->execute();
  }
  return $seat_count;
}

Also you can substract one with database..

Answer 3

Oh boy

function seatCalc($id){

    $stmt=$this->connection->prepare("SELECT seats_left FROM drive WHERE id=:i");
    $stmt->bind_param(":i", $id);
    $stmt->execute();

    $row = $stmt->fetch(PDO::FETCH_ASSOC);
    $seat_count = intval($row['seats_left']);

    if($seat_count > 0){

        $seat_count -= 1;

        $stmt=$this->connection->prepare("UPDATE drive SET seats_left=seats_left-1 WHERE id=:id");
        $stmt->bind_param(":id", $id);
        $stmt->execute();
    }
    return $seat_count;
}