Uncaught Error: Call to undefined method Connection::prepare() in C:xampphtdocsrank-APIappmodelsModel.php:17

class Model
{
    protected $table = "default";
    protected $primaryKey = "id";
    protected $connection;

    function __construct()
    {
        $this->connection = Connection::getConnection();
    }

    public function getAll(){
        try{

            $query = $this->connection->prepare('select * from ' . $this->table);
            $query->execute();

            return $query->fetchAll();

        }catch(PDOException $e){

            echo $e->getMessage();

        }finally{

            $this->connection = null;

        }

    }

}

class Connection
{
    private $host = DB_CONFIG['host'];
    private $database = DB_CONFIG['database'];
    private $user = DB_CONFIG['user'];
    private $pass = DB_CONFIG['pass'];

    private static $connection;


    function __construct()
    {
        try{

            $connection = new PDO("mysql:host=$this->host;dbname=$this->database",
                                    $this->user,
                                    $this->pass);
            $connection->exec("set names utf8");
            $connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

            self::$connection = $connection;


        }
        catch (PDOException $e) {

            echo 'Connection failed: ' . $e->getMessage();

            }
    }

    public static function getConnection(){

        if (self::$connection === null) {
            self::$connection = new self();
        }
        return self::$connection;

    }

}