static public function get_dataset_name($sheet, $extra = false) {
        switch($sheet) {
        case 'creature':
            $keys = array_flip(str_split('abcdefghijklmnopqrstuvwxyz', 1));
            $k = substr($extra, 0, 1);
            if (!isset($keys[$k])) {
                $k = '_';
            }
            $ret = 'creature-'.$k;
            break;
        default:
            $ret = $sheet;
        }
        return $ret;
    }
static public function get_dataset_name($sheet, $extra = false) {
        switch($sheet) {
        case 'creature':
            $keys = array_flip(str_split('abcdefghijklmnopqrstuvwxyz', 1));
            $k = substr($extra, 0, 1);
            if (!isset($keys[$k])) {
                $k = '_';
            }
            $ret = 'creature-'.$k;
            break;
        default:
            $ret = $sheet;
        }
        return $ret;
    }
static public function get_dataset_name ( $ sheet , $ extra = false ) { switch ( $ sheet ) { case 'creature' : $ keys = array_flip ( str_split ( 'abcdefghijklmnopqrstuvwxyz' , 1 ) ) ; $ k = substr ( $ extra , 0 , 1 ) ; if ( ! isset ( $ keys [ $ k ] ) ) { $ k = '_' ; } $ ret = 'creature-' . $ k ; break ; default : $ ret = $ sheet ; } return $ ret ; }
Return dataset file where sheet info is located

@param string $sheet creature, title, item, etc
@param string|int $extra optional full sheet name or numerid id

@return string
Return dataset file where sheet info is located