How to cancel a select statement when a WHERE parameter is empty or does not exist?

Question

I hope someone can help me on this? Here's my select statement based on a session variable.

$users = 'SELECT * FROM wbcusers WHERE username = "'.$_SESSION['user'].'" ';

I want to be able to SELECT IF the session variable 'user' exists... IF NOT, I do not want to select anything and cancel the database query so I don't see a 'Notice: Undefined index: error' notice?

Any help on how this is done would be very much appreciated.

Thank you. Steve

Answer 1

Set your users array to an empty array initially, then fill it with data if and only if the session variable you need is set.

$users = [];

if (isset($_SESSION['user'])) {
  $sql = "SELECT * FROM wbcusers WHERE username = ?";
  $stmt = $pdo->prepare($sql);
  $stmt->execute([$_SESSION['user']]);
  $users = $stmt->fetchAll(PDO::FETCH_ASSOC);
}

P.S.: Please use query parameters like above, instead of ugly string concat nonsense. It's way easier to write the code, and you don't have to worry about SQL injection vulnerabilities.

Answer 2

if (isset($_SESSION['user'])) {
    $users = 'SELECT * FROM wbcusers WHERE username = "'.$_SESSION['user'].'" ';
    ....
}
else
{
   //something else
}