test1/public/drupal-8.3.1/vendor/zendframework/zend-feed/doc/book/find-feeds.md

Feed Discovery from Web Pages

Web pages often contain <link> tags that refer to feeds with content relevant to the particular page. Zend\Feed\Reader\Reader enables you to retrieve all feeds referenced by a web page with one method call:

$feedLinks = Zend\Feed\Reader\Reader::findFeedLinks('http://www.example.com/news.html');

Finding feed links requires an HTTP client

To find feed links, you will need to have an HTTP client available.

If you are not using zend-http, you will need to inject Reader with the HTTP client. See the section on providing a client to Reader.

Here the findFeedLinks() method returns a Zend\Feed\Reader\FeedSet object, which is in turn a collection of other Zend\Feed\Reader\FeedSet objects, each referenced by <link> tags on the news.html web page. Zend\Feed\Reader\Reader will throw a Zend\Feed\Reader\Exception\RuntimeException upon failure, such as an HTTP 404 response code or a malformed feed.

You can examine all feed links located by iterating across the collection:

$rssFeed = null;
$feedLinks = Zend\Feed\Reader\Reader::findFeedLinks('http://www.example.com/news.html');
foreach ($feedLinks as $link) {
    if (stripos($link['type'], 'application/rss+xml') !== false) {
        $rssFeed = $link['href'];
        break;
}

Each Zend\Feed\Reader\FeedSet object will expose the rel, href, type, and title properties of detected links for all RSS, Atom, or RDF feeds. You can always select the first encountered link of each type by using a shortcut: the first encountered link of a given type is assigned to a property named after the feed type.

$rssFeed = null;
$feedLinks = Zend\Feed\Reader\Reader::findFeedLinks('http://www.example.com/news.html');
$firstAtomFeed = $feedLinks->atom;