Simple function for matching any youtube link and grabbing the ID

video_id_from_youtube_url.php

if (!function_exists('video_id_from_youtube_url')):

function video_id_from_youtube_url($source)
{
    $pattern = '/^(?:(?:(?:https?:)?\/\/)?(?:www.)?(?:youtu(?:be.com|.be))\/(?:watch\?v\=|v\/)?([\w\-]+))/is';
    $matches = array();
    preg_match($pattern, $source, $matches);
    if (isset($matches[1])) return $matches[1];
    return false;
}

endif;