Class FixerConverter implements Converter {

    public function loadConversionRate(string $baseCurrency, string $toCurrency): string
    {
        $conversionRateJson = @file_get_contents('http://api.fixer.io/latest?base=' . $baseCurrency . '&symbols=' . $toCurrency));

        if ($conversionRateJson === false) {
            echo 'Error: unexpected error retrieving currency conversion rate from API service.';
        }

        $conversionRateArr = json_decode($conversionRateJson, TRUE);

        $this->conversionRate = $conversionRateArr['rates'][$currency];
    }

    public function convertCurrency(string $amount): float
    {
        if (isset($this->conversionRate)) {
            return $amount * $this->conversionRate;
        }

        echo 'Error: There is no conversion rate loaded.';
    }

}