$stmt = $dbh->prepare("INSERT INTO users (id, username, password, rank_id) VALUES ('', :username, :password, :rank_id)");

$stmt->bindParam(':username', $username);
$stmt->bindParam(':password', $password);
$stmt->bindParam(':rank_id', $rank);

$username = 'TecknoPlay';
$password = md5('P@ssW0rd123');
$rank = 1;
$stmt->execute();