Multi-currency totals

MoneyBag is an immutable multi-currency accumulator — a wallet or basket that keeps balances in several currencies side by side:

use RoundlyConsulting\Money\MoneyBag;

$bag = MoneyBag::of(Money::ofMajor('10', 'EUR'), Money::ofMajor('12', 'USD'))
    ->add(Money::ofMajor('100', 'CZK'))
    ->subtract(Money::ofMajor('2', 'USD'));

$bag->get('USD');         // 10.00 USD
$bag->get('GBP');         // 0.00 GBP — zero when absent
$bag->currencies();       // [CZK, EUR, USD] — sorted by code
$bag->all();              // list<Money>
$bag->isEmpty();          // false

$bag->total('EUR');                    // converted and summed exactly, rounded once
$bag->total('EUR', now()->subDay());   // with historical rates

• of() and add() group amounts by currency code; subtract() works the same way.
• get() returns zero for a currency the bag doesn’t hold.
• currencies() and all() are sorted by code.
• isEmpty() — balances that return to zero drop out of the bag.
• A currency with the same code but a different exponent throws CurrencyMismatch.

Totals without drift

total($in, ?$on, ?$rounding) converts every balance through the bound exchange provider and sums them as one exact rational, rounding once at the end (HalfEven by default) — no per-currency rounding drift. Pass a date to use historical rates.