private function getIndexFieldName(int $depth): string
    {
        if ($depth === 0) {
            return self::$fieldName;
        }

        return sprintf(self::$relatedContentFieldName, $depth);
    }
private function getIndexFieldName(int $depth): string
    {
        if ($depth === 0) {
            return self::$fieldName;
        }

        return sprintf(self::$relatedContentFieldName, $depth);
    }
private function getIndexFieldName ( int $ depth ) : string { if ( $ depth === 0 ) { return self :: $ fieldName ; } return sprintf ( self :: $ relatedContentFieldName , $ depth ) ; }
Returns field name base on given depth.

@param int $depth

@return string
Returns field name base on given depth .