protected function addAuthorizeFields(array &$fields)
{
$fields['USER'] = $this->options['username'];
$fields['PWD'] = $this->options['password'];
$fields['SIGNATURE'] = $this->options['signature'];
if ($this->options['business']) {
$fields['BUSINESS'] = $this->options['business'];
$fields['SUBJECT'] = $this->options['business'];
}
}