$groups = array();
$user_arr = $modx->userLoggedIn();
$web_group = $modx->db->select("webgroup", $modx->getFullTableName('web_groups'), "webuser='".$user_arr['id']."'");
if ($modx->db->getRecordCount($web_group) > 0) {
while ($row = $modx->db->getRow($web_group)) {
$groups[] = $row['web_group'];
}
}
print_r($groups);