if(isset($_POST['register'])) {


    session_start();

    $username=$_POST['username'];
    $password=$_POST['password'];
    $email=$_POST['email'];
    $birthday=$_POST['birthday'];


$sql=$con->query("INSERT INTO users (username, password, email, birthday)VALUES({'$username}', '{$password}', '{$email}', '{$birthday}')";


}