SimplePie sorting multiple feeds - no time/date stamp, no sorting?

Question

Is there a way to force an array of feeds to sort on date, even if one feed is missing a time/date stamp?

If I understand correctly, one bad feed in the list messes up sorting. From the description of the SimplePieWP plugin, but presumably a general issue:

'... the plugin also supports what we affectionately call “Multifeeds”. This allows you to >merge multiple feeds together and sort the items by time and date ... notice that I said >“sort the items by time and date.” So, what happens if a feed is missing a time/date->stamp? They won't sort. (Duh.) Sorting by date requires ALL individual items in ALL merged >feeds to have time/date-stamps associated with them.'

I think I regularly see the result of this in my sites; feeds are not sorted on date, posts from the top feed in the array are always at the top etc.

In my set-up it is impossible to manually check each feed for a time/date stamp; the feed lists are too long and/or constantly changing and automatically generated.

Is there code I can add somewhere to just filter out feeds without time/date stamps?

Or to give bad feeds a default time/date in the 1970s, so they sort at the bottom?

Or has this issue already been fixed? Am I missing something?

I've done many searches on this over the years, but have never figured it out.

Answer 1

SimplePie does an explicit check of each item in SimplePie::merge_items() to determine if any item is missing a date.

You will have to override this method to change sorting behavior for multifeeds. Below is an override to sort multifeeds even when items are missing a date. If the item is missing a date, it is sorted to the bottom. (using SimplePie 1.3).

class SimplePieAlwaysSort extends SimplePie
{
  public function get_items($start = 0, $end = 0)
  {
    if (!isset($this->data['items']))
    {
      if (!empty($this->multifeed_objects))
      {
        $this->data['items'] = self::merge_items($this->multifeed_objects, $start, $end, $this->item_limit);
      }
    }

    return parent::get_items($start, $end);
  }

  public static function merge_items($urls, $start = 0, $end = 0, $limit = 0)
  {
    if (is_array($urls) && sizeof($urls) > 0)
    {
      $items = array();
      foreach ($urls as $arg)
      {
        if ($arg instanceof SimplePie)
        {
          $items = array_merge($items, $arg->get_items(0, $limit));
        }
        else
        {
          trigger_error('Arguments must be SimplePie objects', E_USER_WARNING);
        }
      }

      usort($items, array(get_class($urls[0]), 'sort_items'));

      if ($end === 0)
      {
        return array_slice($items, $start);
      }
      else
      {
        return array_slice($items, $start, $end);
      }
    }
    else
    {
      trigger_error('Cannot merge zero SimplePie objects', E_USER_WARNING);
      return array();
    }
  }
}

$pie = new SimplePieAlwaysSort();
$pie->set_feed_url(array('http://stackoverflow.com/feeds'));
$pie->init();

foreach ($pie->get_items() as $item)
{
  // do stuff
}