Class "app\models\PDO" not found при execute

Пишу мини CRM на PHP в ООП стиле, делаю st->prepare, прокидываю бинды, делаю execute, и мне выдает такую ошибку:

Fatal error: Uncaught Error: Class "app\models\PDO" not found in /var/www/PHP/Mini CRM (Андрей Андриевский)/app/models/UserModel.php:39 Stack trace: #0 /var/www/PHP/Mini CRM (Андрей Андриевский)/app/controllers/users/UsersController.php(43): app\models\UserModel->create() #1 /var/www/PHP/Mini CRM (Андрей Андриевский)/app/Router.php(28): app\controllers\users\UsersController->store() #2 /var/www/PHP/Mini CRM (Андрей Андриевский)/index.php(13): app\Router->run() #3 {main} thrown in /var/www/PHP/Mini CRM (Андрей Андриевский)/app/models/UserModel.php on line 39

Вот код:

<?php

namespace app\models;

use app\controllers\users\UsersController;
use app\models\DatabaseModel;

class UserModel
{

    private $db;

    public function __construct()
    {
        $this->db = DatabaseModel::getInstance()->getConnection();
    }

    public function readAll()
    {

        $st = $this->db->prepare("SELECT * FROM users");
        $st->execute();

        $users = $st->fetchAll();

        return $users;

    }

    public function create($data)
    {

        $login = $data['login'];
        $password = password_hash($data['password'], PASSWORD_DEFAULT);
        $password_confirm = $data['password_confirm'];
        $is_admin = isset($data['is_admin']) ? 1 : 0;

        $st = $this->db->prepare("INSERT INTO users (login, password, is_admin) VALUES (?, ?, ?)");
        $st->bindParam(1, $login, PDO::PARAM_STR);
        $st->bindParam(2, $password, PDO::PARAM_STR);
        $st->bindParam(3, $is_admin, PDO::PARAM_INT);
        $st->execute();

    }
}