PHP
<?php
$url = $_GET['link'];
$getcontents = file_get_contents($url);
$thumbnailUrl = explode('<link itemprop="thumbnailUrl" href="', $getcontents)[1];
$thumbnailUrlResult = explode('">', $thumbnailUrl)[0];
if(!$thumbnailUrlResult) {
echo 'YouTube Link falsch eingegeben.';
exit;
}
?>
