Randomizing the RSS Widget

Question

I'm trying to see if there's a way I can make it where the RSS widget can pull in a different feed (one of let's say ten I pick) and displays it in the widget each time the page is refreshed?

It's kind of like this post (Different rss feeds in a single dashboard widget) except this person is trying to display several feeds at once and I want to rotate it from one feed to another each time you refresh the page or go to a different page. So it only displays one feed, but it's different every time.

Answer 1

Here's one way to achieve this:

/**
 * Display a random feed in the RSS Widget
 * Activated by the wpse_random_url string in the feed url
 *
 * @see http://wordpress.stackexchange.com/a/187599/26350
 */

! is_admin() && add_filter( 'wp_feed_options', function( $feed, $url )
{
    // Modify this list of feeds to your needs:
    $urls = [
        'http://stackoverflow.com/feeds/', 
        'http://wordpress.stackexchange.com/feeds',
        'http://unix.stackexchange.com/feeds'
    ];

    // Select a random feed from the above list:            
    if(    class_exists( '\SimplePie' )
        && $feed instanceof \SimplePie 
        && false !== strpos( $url, 'wpse_random_url' ) 
        && method_exists( $feed, 'set_feed_url' ) 
    )
            $feed->set_feed_url( $urls[ array_rand( $urls ) ] );

    return $feed;
}, 10, 2 );

where our feed url must contain the wpse_random_url string.

We could for example use our current site's feed, with the random_url GET parameter:

http://example.tld/feed/?wpse_random_url

and add that to the url field of the RSS widget:

The next step to improve this mini plugin, would be to introduce a way to add the list of feeds, directly from the backend instead of having to modify it within the code itself.