src/ConfigProvider.php
private function retrieveConfigurationValues(array $options): array
    {
        $outputValues = [];

        foreach ($options as $option) {
            $value = getenv($option);

            // value was not retrieved => fail
            if ($value === false) {
                throw new \RuntimeException(sprintf('%s environment variable must be defined', $option));
            }

            $outputValues[Inflector::camelize(mb_strtolower($option))] = $value;
        }

        return $outputValues;
    }
private function retrieveConfigurationValues(array $options): array
    {
        $outputValues = [];

        foreach ($options as $option) {
            $value = getenv($option);

            // value was not retrieved => fail
            if ($value === false) {
                throw new \RuntimeException(sprintf('%s environment variable must be defined', $option));
            }

            $outputValues[Inflector::camelize(mb_strtolower($option))] = $value;
        }

        return $outputValues;
    }
Retrieve given configuration options values from environment. If value is not found, throw and exception.

@throws \RuntimeException
@return array Option => value option name is converted from CAPS_WITH_UNDERSCORES to camelCase