if (sizeof($errors) === 0) {
    if (isset($_POST["register"])) {

        $sql = $db->prepare(
            "SELECT 1
            FROM users
            WHERE username = :username");
            $sql->bindParam(":username", $_POST["username"]);
            $sql->execute();

            $data = $sql->fetch();
            $usernameFree = isset($data);


        if (!$usernameFree) {
            die('Username taken');
        } else {
            $sql = $db->prepare(
            "INSERT INTO users (username, password)
            VALUES (:username, :password)");
            $sql->bindParam(":username", $_POST["username"]);

            $password = passwordHash($_POST["password"]);
            $sql->bindParam(":password", $password);
            $sql->execute();

            $_SESSION["logged"] = true;
        }
    }
}