this script produces error: 
parse error ,expecting ?')" in ... on line ... 

  if (!empty($t_dtd->get('group_field'))) {    
        $group_field = 'v'.$t_dtd->get('group_field');
        if (!empty($t_dtd->get('group_func'))){
	$group_func = "g_fn_".$t_dtd->get('group_func');
        }else{     
	$group_func = "g_fn_base";
        }   
  }    


this one is ok

$t = $t_dtd->get('group_field');
if (!empty($t)) {    
      $group_field = 'v'.$t_dtd->get('group_field');    
      $t = $t_dtd->get('group_func');
      if (!empty($t)){
     	$group_func = "g_fn_".$t_dtd->get('group_func');
      }else{ 
	$group_func = "g_fn_base";    
     }   
}