<?php
error_reporting(E_ALL);
$feedURL = 'https://www.googleapis.com/youtube/v3/search?part=snippet&channelId=yyy&maxResults=3&order=date&type=video&key=xxx';
$sxml = simplexml_load_file($feedURL);
$i=0;
foreach ($sxml->entry as $entry) {
      $media = $entry->children('media', true);
      $watch = (string)$media->group->player->attributes()->url;
      $thumbnail = (string)$media->group->thumbnail[0]->attributes()->url;
      ?>
      <div class="videoitem">
        <div class="videothumb"><a href="<?php echo $watch; ?>" class="watchvideo"><img src="<?php echo $thumbnail;?>" alt="<?php echo $media->group->title; ?>" /></a></div>
        <div class="videotitle">
            <h3><a href="<?php echo $watch; ?>" class="watchvideo"><?php echo $media->group->title; ?></a></h3>
            <p><?php echo $media->group->description; ?></p>
        </div>
      </div>      
<?php $i++; if($i==3) { echo '<div class="clear small_v_margin"></div>'; $i=0; } } ?>

Importante conoscere la chiave API di Google per Youtube e l’identificativo del canale da cui estrarre la lista

RSS Ultimi video Yotube da canale

https://www.googleapis.com/youtube/v3/search?part=snippet&channelId={CHANNEL_ID}&maxResults=10&order=date&type=video&key={YOUR_API_KEY}