PHP - Calling Multiple Functions In Single Call From Class

I am currently building my own MVC Framework and I have run into an issue that I can't solve when attempting to use 2 methods from a single model. I know that this isn't an issue with the queries or information being return. I am unsure of the proper way that I can call 2 methods when checking to see if a user is logged in... The issue that I face is both methods are calling the DB and it throws a PDO error which I don't know how to get around the issue.. Any guidance would be nice as I have been banging my head over this issue. Thank you!

Fatal error: Uncaught Error: Call to undefined method PDO::Select() in C:\xampp\htdocs\PicWrist\app\models\user.class.php:318 Stack trace: #0 C:\xampp\htdocs\PicWrist\app\controllers\home.php(21): User->getUser('4') #1 C:\xampp\htdocs\PicWrist\app\core\app.php(36): Home->index() #2 C:\xampp\htdocs\PicWrist\app\init.php(47): App->__construct() #3 C:\xampp\htdocs\PicWrist\public\index.php(5): require('C:\\xampp\\htdocs...') #4 {main} thrown in C:\xampp\htdocs\PicWrist\app\models\user.class.php on line 318

//Controller

<?php 
	/**
	 * Load the View
	 */
	class Controller{

		public function view($view, $data = []) {
			if (file_exists('../app/views/' . $view . '.php')) {
				require_once '../app/views/' . $view . '.php';
			} 
		}

		public function model($model, $data = []) {

			if (file_exists('../app/models/' . $model . '.class.php')) {
				require_once '../app/models/' . $model . '.class.php';

				return new $model();

			} else 

				return false;
		}
	}

?>

//Home Controller
<?php 
Class Home extends Controller {

	public static $user;
	public $errors;

	public function __construct() {

		self::$user = $this->model('user');

	}

	public function index() {
		$userdata 			= [];
		$data				= [];

		show(self::$user);
		$isLoggedin	= self::$user->isLoggedin;
		show($isLoggedin);

		$userdata = self::$user->getUser($_SESSION['user_id']);
		show($userdata);

		$this->view('home', $data);
	}

}

?>
<?php 
/**
 * Users
 */
class User
{
	private $db;
	private $errors = '';
	public $isLoggedin = False;
	public $isAdmin = False;

	public function __construct() {
		$this->isLoggedIn();
	}

	public function isLoggedIn() {

		if(isset($_SESSION['user_id'])){

			$data['user_id'] = $_SESSION['user_id'];
			$db = Database::getInstance();
			$query = "SELECT * FROM users WHERE user_id = :user_id LIMIT 1";
			$results = $db->Select($query, $data);

			if (is_array($results)) {
				 $this->isLoggedIn = True;
			}
		}

	}


	public function getUser($id) {

		if(isset($id)) {

			$data['user_id']	= intval($id);
			$db 				= Database::getInstance();
			$query 				= 'SELECT * FROM users WHERE user_id = :user_id';

			$results = $db->Select($query, $data);

			if (is_array($results)) {
				return $results;
			} else {
				return False;
			}
		} else {
			return False;
		}
	}

//DB
<?php 
	/**
	 * Database Connection
	 */
	class Database	{
		private $dbHost = DB_HOST;
		private $dbUser = DB_USER;
		private $dbPass = DB_PASS;
		private $dbName = DB_NAME;

		private $statment;
		private static $dbHandler;
		private $error;

		public function __construct()
		{
			$conn = 'mysql:host=' . $this->dbHost . ';dbname=' . $this->dbName;

			$options = array(
				PDO::ATTR_PERSISTENT 	=> true,
				PDO::ATTR_ERRMODE 		=> PDO::ERRMODE_EXCEPTION
			);

			try {
				self::$dbHandler = new PDO($conn, $this->dbUser, $this->dbPass, $options);
			} catch (PDOException $e) {
				self::$error = $e->getMessage();
				echo self::$error;
			}
		}

		public static function getInstance() {

			if(self::$dbHandler) {
				return self::$dbHandler;
			}

			return $instance = new Self();
		}

		public function Select($query, $data = array()) {
			$statement = self::$dbHandler->prepare($query);
			$result	= $statement->execute($data);

			If($result) {
				$data = $statement->fetchAll(PDO::FETCH_OBJ);
					if(is_array($data)) {
						// show($data);
						return $data;
				}
			}

			return False;
		}

		public function Update($query, $data = array()) {
			$statement = self::$dbHandler->prepare($query);
			$result	= $statement->execute($data);

			If($result) {
				return True;
			} 
			
			return False;

		}

	}

?>

Hi All

I have not really played around with PHP in ages so I am having a hard time trying to figure out the best way to proceed. Anyhow... what I need to get done is to take a singleton pattern core database class that has a extended driver based class (ie; the type of database server the connection is connecting to), and build a new class that dynamically handles as many driver based connections that are called using a single instance. As a side note, I tried PDO but it only supports a single driver per class instance, and then each of those connections cannot not have their on set of properties that relate to each connection. Anyway, I was thinking that the best way to handle all the driver specific connections, is to hand out a 'unique hash reference' that points to an array of connection objects and the object properties. then when the client runs any sql function they pass the 'unique hash reference'  which the class then returns the object and it properties that will be used by the class to call up the driver specific sql function that was requested by the client. So what do you all thing about that....

TIA

stephanieT

PS...

I reason i need this is because I need to update up 25 different databases based on data stored on all the databases and  not all of the database servers are of the same type, (ie; MSSQL, Oracle, MySQL, MariaDB, berkeley DB, postgres, sqlite2,3, etc, etc)!