Eko\FeedBundle\Formatter\Formatter::formatMediaItemField PHP Method

    protected function formatMediaItemField(MediaItemField $field, ItemInterface $item)
    {
        $elements = [];
        $method = $field->getMethod();
        $values = $item->{$method}();
        if (null === $values) {
            return $elements;
        }
        if (!is_array($values) || is_array($values) && isset($values['value'])) {
            $values = [$values];
        }
        foreach ($values as $value) {
            if (!isset($value['type']) || !isset($value['length']) || !isset($value['value'])) {
                throw new \InvalidArgumentException('Item media method must returns an array with following keys: type, length & value.');
            }
            $elementName = $field->getName();
            $elementName = $elementName[$this->getName()];
            $element = $this->dom->createElement($elementName);
            $this->addAttributes($element, $field, $item);
            switch ($this->getName()) {
                case 'rss':
                    $element->setAttribute('url', $value['value']);
                    break;
                case 'atom':
                    $element->setAttribute('rel', 'enclosure');
                    $element->setAttribute('href', $value['value']);
                    break;
            }
            $element->setAttribute('type', $value['type']);
            $element->setAttribute('length', $value['length']);
            $elements[] = $element;
        }
        return $elements;
    }