Answer by Cameron Hurd for Reversing sort order of ingested RSS feed in PHP

Try the appropriately named array_reverse function!

<?php if(function_exists('fetch_feed')) {    include_once(ABSPATH . WPINC . '/feed.php'); // include the required file    $feed = fetch_feed('http://sample.com.au/events/feed/');  // specify the source feed    $limit = $feed->get_item_quantity(25); // specify number of items    $items = $feed->get_items(0, $limit); // create an array of items     $semti = array_reverse($items); // & flip it}if ($limit == 0) echo '<div>The feed is unavailable.</div>';else foreach ($semti as $item) : ?><p><b><a href="<?php echo esc_url( $item->get_permalink() ); ?>" target="_blank"><?php echo esc_html( $item->get_title() ); ?></a></b><?php echo esc_html( $item->get_date('| j F | g:i a') ); ?><br><?php echo sanitize_text_field( $item->get_content() ); ?></p>  <?php endforeach; ?>

From PHP.net:

array_reverse

Return an array with elements in reverse order

array array_reverse ( array $array [, bool $preserve_keys = false ] )

Takes an input array and returns a new array with the order of the elements reversed.