Regex to parse a youtube URL and extract the video id

gistfile1.php

<?php
    public static function getYoutubeVideoIdFromUrl($url)
    {
        // Check for a valid youtube url
        $rx = '~                                                # Using ~ to avoid LTS (http://en.wikipedia.org/wiki/Leaning_toothpick_syndrome)
                ^http(?:s)?://                                  # Mandatory protocol (optional ssl)
                (?:www\.)?                                      # Optional subdomain
                (?:youtube\.com/watch(?:/)?\?v=|youtu\.be/)     # mandatory domain & path for youtube or shortlink for youtu.be
                ([^?&]+)                                        # video id as capture group 1
                ~x';
        $has_match = preg_match($rx, $url, $matches);
        if ($has_match)
        {
            return $matches[1];
        }

        return false;
    }