How do I solve “Parameter must be an array or an object that implements Countable?” [duplicate]

Answer 1

As a matter of fact, you never need to count anything. This step is just redundant.

If you give it a bit of a thought, you can simply fetch your data first and then use it in the condition. What is much more important, you must use a parameterized query. So the code should be

$stmt = $mysqli->prepare("SELECT * FROM isalonusers WHERE user_id=?");
$stmt->bind_param("i", $id);
$stmt->execute();
$result = $stmt->get_result();
// here goes your problem with "count" 
$row = $result->fetch_array(MYSQLI_ASSOC)
if($row) {
    $username = $row['username'];
    $password = $row['password'];
}

Neither should you use that terrible practice with or die

Answer 2

How about this way with $result->num_rows?

if(isset($_GET['edit'])){
    $id = $_GET['edit'];
    $update = true;
    $result = $mysqli->query("SELECT * FROM isalonusers WHERE user_id=$id") or die($mysqli->error);
    if(isset($result->num_rows) && $result->num_rows > 0){
        $row = $result->fetch_array(MYSQLI_ASSOC);
        $username = $row['username'];
        $password = $row['password'];
    }
  }

See ref.: http://php.net/manual/en/mysqli.query.php