get youtube thumbnail from content

get-thumbnail-youtube

<?php 
/* Get thumbnail from Video Embed code */
function nesia_get_video_image() {
    global $post;

    if (preg_match('%(?:youtube(?:-nocookie)?\.com/(?:[^/]+/.+/|(?:v|e(?:mbed)?)/|.*[?&]v=)|youtu\.be/)([^"&?/ ]{11})%i', $post->post_content, $match)) {
        $video_id = $match[1];
    } else {
        return false;
    }

    // YouTube - get the corresponding thumbnail images
    if( isset($video_id) )
        $video_thumb = "http://img.youtube.com/vi/".$video_id."/0.jpg";

    // return whichever thumbnail image you would like to retrieve
    return $video_thumb;
}
?>