private function __construct() {
            $servername = "localhost";
            $username = "root";
            $password = "";
            $dbname = "myDB";
            $this->msg = new Messages();
try {
// assign PDO object to db variable
self::$db = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
self::$db->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
// echo "Connected successfully";
}