Caching seems not to work - multi feed - rss

Question

I use simplepie to merge rss feeds. I have two sections on this page which do the same with different feeds. i sort them. here is my code:
$feeds=array(
'http://feeds.feedburner.com/Belvederegasse',
'http://diealternative.org/zeitschrift/feed/rss/',
'http://diealternative.org/arbeitsklima/feed/rss/',
'http://feeds.feedburner.com/Arbeitszeit',
'http://feeds.feedburner.com/AugeFinance',
'http://diealternative.org/nulllohnrunden/feed/',
'http://diealternative.org/bulletin/feed/rss/',
'http://feeds.feedburner.com/verteilungsgerechtigkeit',
'http://feeds.feedburner.com/hochschule',
'http://feeds.feedburner.com/Sozialmilliarde'
);
$first_items = array();
foreach ($feeds as $url)
{
$feed = new SimplePie();
$feed->set_stupidly_fast(true);
$feed->enable_order_by_date(true);
$feed->enable_cache(true);
$feed->set_feed_url($url);
$feed->init();
$items_per_feed = 5;
for ($x = 0; $x < $feed->get_item_quantity($items_per_feed); $x++){
$first_items[] = $feed->get_item($x);
}
unset($feed);
}
function sort_items($a, $b){
return SimplePie::sort_items($a, $b);
}
usort($first_items, "sort_items");
foreach ($first_items as $item):
if ($itemlimit==8) { break; }
//HTML output
$itemlimit = $itemlimit + 1;
endforeach;
?>
When you visit the page http://diealternative.org it takes more than 20 seconds to load. Thats no surprise because there are lots of feeds to parse but whats about the caching? After once loaded it should not reconnect to the feeds, it should use the cache.
Why it takes so long every time to load.

Answer 1

A couple things: First, by default it only caches for 60 minutes I think - I set mine to 24 hours so that it saves the cache for the whole day. The first load is slow, but speeds up after that. Also, the set_stupidly_fast function may possibly disable caching or something.
Secondly, SimplePie will merge the feeds for you and sort by date, you don't need a nested loop like that. Try this:
$max_items_per_feed = 5; // this pulls the top 5 articles from each feed
$max_items_total = 50; // this caps the total articles
$feed = new SimplePie();
$feed->set_feed_url($feeds);
// limit the number of items
$feed->set_item_limit($max_items_per_feed);
$feed->enable_cache(true);
$feed->set_cache_duration(86400); // refresh cache once a day - 24 hrs
// Run SimplePie.
$success = $feed->init();
// This makes sure that the content is sent to the browser as text/html and the UTF-8 character set (since we didn't change it).
$feed->handle_content_type();
foreach ($feed->get_items(0, $max_items_total) as $key=>$item) {
...
}

Answer 2

What worked for me is to use Simplepie to generate separately html files. These i save to the server and include them on the main page. By using cronjobs I keep them updating.
The loading time of the website is now good. (up to 150% faster!)
tom