Rss feed filter SimplePie

Hi,
I'm rather new to php so...I use simplepie to parse rss feed but i want to filter them by keywords
i made this code :

$feed = new SimplePie(); 
$feed->set_feed_url(http://website.name/rss); 
$feed->init(); 
$feed->set_cache_duration (3600); 
$feed->set_timeout(30); 
$feed->handle_content_type(); 
$countItem = 0; 
foreach ($feed->get_items() as $item){ 
$checktitle = $item->get_permalink(); 
//Regex keyword filter 
$pattern = '/keyword1|keyword2/'; 
//If the there is a keyword match, store in $matches array 
if (preg_match($pattern, $checktitle)) { 
        $news[$countItem]= $item; 
        $countItem++; 
} 
}  

This is the filtering part it does it work but, i want all the items that contains both keywords.
I'm not sure that preg_match is the right way to do this but it;s the only thing i got, so please!