Почему не подключается PDO?

Uncaught PDOException: SQLSTATE[HY000] [2019] Unknown character set

class connectDB
	 {
	 	private $host = 'localhost';
	 	private $user = 'root';
	 	private $password = '';
	 	private $db = 'registration';
	 	private $charset = 'utf-8';
	 	private $opt = [
	 		PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
	 		PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
	 		PDO::ATTR_EMULATE_PREPARES   => false,
	 		];
	 	public $pdo;
	 	public function connect()
	 	{
	 			$this->pdo = new PDO("mysql:host=$this->host;dbname=$this->db;charset=$this->charset",$this->user,$this->password,$this->opt);


	 	}

	 	public function close_connect()
	 	{
	 		$this->pdo = null;
	 	}
	 }