Fatal error: Call to a member function getElementsByTagName() WordPress 4.2.2 RSS Feed

Solution:

You can use this way :

$feed = new DOMDocument();
$feed->load('http://www.revolutionpersonaltraining.com.au/blog/feed/');


$items = array();
foreach ($feed->getElementsByTagName('item') as $item) {
    array_push($items, array ( 
        'title' => $item->getElementsByTagName('title')->item(0)->nodeValue,
        'desc' => $item->getElementsByTagName('description')->item(0)->nodeValue,
        'link' => $item->getElementsByTagName('link')->item(0)->nodeValue,
        'date' => $item->getElementsByTagName('pubDate')->item(0)->nodeValue,
    ));
}

Good Luck