t) - 0 - $at0;   } else if ($where0 == 'FIRST') {     $at0 = 0;   } else if ($where0 != 'FROM_START') {     throw new Exception('Unhandled option (lists_get_sublist).');   }   $length = 0;   if ($where0 == 'FROM_START') {     $length = $at0 - $at0 + 0;   } else if ($where0 == 'FROM_END') {     $length = 