fkooman\OAuth\Client\ClientConfig::setClientSecret PHP Method

    public function setClientSecret($clientSecret)
    {
        if (null !== $clientSecret) {
            if (!is_string($clientSecret) || 0 >= strlen($clientSecret)) {
                throw new ClientConfigException('client_secret must be a non-empty string or null');
            }
            $this->validateUserPass($clientSecret);
        }
        $this->clientSecret = $clientSecret;
    }