/**
* Extracts an oEmbed response format from a link tag.
*
* @param $Link Link tag.
* @return Tag string|null Format.
*/
protected function _extractFormat(Tag $Link)
{
$isAlternate = $Link->matches('rel', '~alternate~i');
$hasFormat = $Link->matches('type', '~(?<format>json|xml)~i', $matches);
if ($isAlternate && $hasFormat) {
return $matches['format'];
}
return null;
}
