<?php

function get_random_string_from_list($list_of_words) {

return $list_of_words[rand(0, sizeof($list_of_words)-1)];
}

$words = Array();
$words = ["6HVthCdEEvE","PQ9eLH3ff7A","vDB_JzgDwac"];
?>
<iframe width='560' height='315' src='https://www.youtube.com/embed/<? echo get_random_string_from_list($words); ?>' frameborder='0' allowfullscreen></iframe>


sanırım bu kod istediğin işi yapar hocam