Call to a member function prepare() on null use oop classes - php

Question

In DB.class.php this is my database constructor"
private $database;
private $error;
private $stmt;
public function __construct()
{
$dsn = ...;
$options = array (
PDO::ATTR_PERSISTENT => true,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
);
try {
$this->database = new PDO("$dsn, $this->user, $this->pass, $options");
} catch ( PDOException $e ) {
echo "error";
}
}
public function builder(string $sql)
{
$this->stmt = $this->database->prepare($sql);
$this->stmt->execute();
if (!$stmt) {
exit("Database query failed . . . !");
}
return $stmt;
}
and this is my User.class.php which is extended, my database class:
public function logIn()
{
$sql = "SELECT...;"
$login = parent::builder($sql);
//vardump($login);
$data = $login->fetch(PDO::FETCH_ASSOC);
if ($login->rowCount() == 1) {
$_SESSION['id'] = $data['id'];
Redirect::to('index.php');
} else {
echo "Incorrect user and pass . . .";
exit();
}
}
this is my child constructor
public function __construct(array $args = [])
{
$this->username = $args['username'] ?? '';
$this->email = $args['email'] ?? '';
$this->phone_number = $args['phone_number'] ?? '';
$this->password = $args['password'] ?? '';
$this->photo = $args['photo'] ?? '';
$this->gender = $args['gender'] ?? '';
}
when I var dump $login I get an error ((Uncaught Error: Call to a member function prepare() on null)) how can I fix this problem?