public function GetHttpHeaderBasicKey()
    {
        if (is_null($this->_root->Config->ClientId) || strlen($this->_root->Config->ClientId) == 0) {
            throw new Exception('MangoPayApi.Config.ClientId is not set.');
        }
        
        if (is_null($this->_root->Config->ClientPassword) || strlen($this->_root->Config->ClientPassword) == 0) {
            throw new Exception('MangoPayApi.Config.ClientPassword is not set.');
        }
        
        $signature = $this->_root->Config->ClientId . ':' . $this->_root->Config->ClientPassword;
        return base64_encode($signature);
    }