PDO in class not executing
public function loginUser(PDO $db, $email, $password)
{
        $this->_db = $db;
        $this->_email = $email;
        $this->_password = $password;

    $user = $this->_checkCredentials();
    if ($user) {
        $this->_user = $user; // store it so it can be accessed later
        return $user['id'];
    }

    return false;
}

protected function _checkCredentials()
{
    $stmt = $this->_db->prepare('SELECT * FROM member WHERE email = ? AND password = ?');
    $stmt->execute(array($this->_email, $this->_password));
    if ($stmt->rowCount() > 0) {
        $user = $stmt->fetch(PDO::FETCH_ASSOC);
        return $user;
    }
    return $stmt->debugDumpParams();
}

$userService = new UserService();
if ($user_id = $userService->loginUser($pdo, 'user@mail.com', 'userpass')) {
    echo 'Logged it as user id: '.$user_id;
    $userData = $userService->getUser();
    // do stuff
} else {
    echo 'Invalid login';
}