src/Credentials/CredentialsProvider.php
public static function env()
    {
        return function () {
            $appId = getenv(self::ENV_APP_ID);
            $certId = getenv(self::ENV_CERT_ID);
            $devId = getenv(self::ENV_DEV_ID);

            if ($appId && $certId && $devId) {
                return new Credentials($appId, $certId, $devId);
            } else {
                return new \InvalidArgumentException(
                    'Could not find environment variable '
                    . 'credentials in '. self::ENV_APP_ID . '/'
                    . self::ENV_CERT_ID . '/'
                    . self::ENV_DEV_ID
                );
            }
        };
    }
public static function env()
    {
        return function () {
            $appId = getenv(self::ENV_APP_ID);
            $certId = getenv(self::ENV_CERT_ID);
            $devId = getenv(self::ENV_DEV_ID);

            if ($appId && $certId && $devId) {
                return new Credentials($appId, $certId, $devId);
            } else {
                return new \InvalidArgumentException(
                    'Could not find environment variable '
                    . 'credentials in '. self::ENV_APP_ID . '/'
                    . self::ENV_CERT_ID . '/'
                    . self::ENV_DEV_ID
                );
            }
        };
    }
Provider that creates credentials from environment variables
EBAY_SDK_APP_ID, EBAY_SDK_CERT_ID, and EBAY_SDK_DEV_ID.

@return callable