public function updateBalance($amount)
{
$this->balance += $amount;
}
public function giveMoney(User $receiver, $amount)
{
if ($this->balance < $amount || $amount <= 0) {
// Кидай ошибку
} else {
$this->balance -= $amount;
$receiver->updateBalance($amount);
//Ура, зелень ушла
}
}