src/Fields/Field.php
protected function toString($codes, $options = [])
    {
        $glue = isset($options['glue']) ? $options['glue'] : static::$glue;
        return $this->clean(implode($glue, $this->getSubfieldValues($codes)), $options);
    }
protected function toString($codes, $options = [])
    {
        $glue = isset($options['glue']) ? $options['glue'] : static::$glue;
        return $this->clean(implode($glue, $this->getSubfieldValues($codes)), $options);
    }
protected function toString ( $ codes , $ options = [ ] ) { $ glue = isset ( $ options [ 'glue' ] ) ? $ options [ 'glue' ] : static :: $ glue ; return $ this -> clean ( implode ( $ glue , $ this -> getSubfieldValues ( $ codes ) ) , $ options ) ; }
Return concatenated string of the given subfields.

@param string[] $codes
@param array    $options
@return string
Return concatenated string of the given subfields .