youtube_thumb.php

<?php
/**
*   Youtube link embed conversion
*	
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/0.jpg
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/1.jpg
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/2.jpg
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/3.jpg
*
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/default.jpg
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/hqdefault.jpg
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/mqdefault.jpg
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/sddefault.jpg
*	https://img.youtube.com/vi/<insert-youtube-video-id-here>/maxresdefault.jpg
*
*/
$video = preg_replace("/\s*[a-zA-Z\/\/:\.]*youtube.com\/watch\?v=([a-zA-Z0-9\-_]+)([a-zA-Z0-9\/\*\-\_\?\&\;\%\=\.]*)/i","//www.youtube.com/embed/$1", $youtube_link);
$thumb = preg_replace("/\s*[a-zA-Z\/\/:\.]*youtube.com\/watch\?v=([a-zA-Z0-9\-_]+)([a-zA-Z0-9\/\*\-\_\?\&\;\%\=\.]*)/i","//img.youtube.com/vi/$1/maxresdefault.jpg", $youtube_link);

// no controls
$youtube_embed = preg_replace("/\s*[a-zA-Z\/\/:\.]*youtube.com\/watch\?v=([a-zA-Z0-9\-_]+)([a-zA-Z0-9\/\*\-\_\?\&\;\%\=\.]*)/i","//www.youtube.com/embed/$1?rel=0&amp;controls=0&amp;showinfo=0", $youtube_link);

?>

<iframe width="100%" height="400" src="<?=$video?>" frameborder="0" allowfullscreen></iframe>

<img src="<?=$thumb?>" alt="" />