$visitor = XenForo_Visitor::getInstance();
if ($visitor['gender'] == "male")
{
$dw = XenForo_DataWriter::create('XenForo_DataWriter_User');
$dw->setExistingData($visitor['user_id']);
$dw->set('style_id', '3');
$dw->save();
}
if ($visitor['gender'] == "female")
{
$dw = XenForo_DataWriter::create('XenForo_DataWriter_User');
$dw->setExistingData($visitor['user_id']);
$dw->set('style_id', '1');
$dw->save();
}