use Swap\Builder;

// Build Swap
$swap = (new Builder())

    // Use the Fixer service as first level provider
    ->add('apilayer_fixer', ['api_key' => 'Get your key here: https://fixer.io/'])
     
    // Use the currencylayer service as first fallback
    ->add('apilayer_currency_data', ['api_key' => 'Get your key here: https://currencylayer.com'])
    
    // Use the exchangerates service as second fallback
    ->add('apilayer_exchange_rates_data', ['api_key' => 'Get your key here: https://exchangeratesapi.io/'])
->build();
    
// Get the latest EUR/USD rate
$rate = $swap->latest('EUR/USD');

// 1.129
$rate->getValue();

// 2016-08-26
$rate->getDate()->format('Y-m-d');

// Get the EUR/USD rate 15 days ago
$rate = $swap->historical('EUR/USD', (new \DateTime())->modify('-15 days'));