PHP Wallet : Perform operations with amounts in a wallet

Example Usage:

try {
    $walletA = new DigitalWallet(100);
    $walletB = new DigitalWallet(50);

    $walletA->deposit(30);
    $walletB->withdraw(20);

    echo "Wallet A Balance: " . $walletA->getBalance() . "<br>";
    echo "Wallet B Balance: " . $walletB->getBalance() . "<br>";

    $walletA->transfer($walletB, 25);

    echo "Wallet A Balance after transfer: " . $walletA->getBalance() . "<br>";
    echo "Wallet B Balance after transfer: " . $walletB->getBalance() . "<br>";
} catch (Exception $e) {
    echo "Error: " . $e->getMessage();
}