Max PHP

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

    $username = $_POST["username"];
    $password = $_POST["password"];
    $database = "DB.txt";

    $userdata = "Username: " . $username . " | Password: " . $password .
    password_hash($password, PASSWORD_DEFAULT);

    file_put_contents($database, $userdata, FILE_APPEND);

}