PHP を使用して URL から YouTube ビデオ ID を抽出する方法

<code class="php">function youtube_id_from_url($url) {
    $pattern = '%^
        (?:https?://)?  # Optional scheme. Either http or https
        (?:www\.)?      # Optional www subdomain
        (?:             # Group host alternatives
          youtu\.be/    # Either youtu.be,
        | youtube\.com  # or youtube.com
          (?:           # Group path alternatives
            /embed/     # Either /embed/
          | /v/         # or /v/
          | /watch\?v=  # or /watch\?v=
          )             # End path alternatives.
        )               # End host alternatives.
        ([\w-]{10,12})  # Allow 10-12 for 11 char youtube id.
        $%x';
    $result = preg_match($pattern, $url, $matches);
    if ($result) {
        return $matches[1];
    }
    return false;
}</code>

<code class="php">$video_id = youtube_id_from_url('http://youtu.be/NLqAF9hrVbY');
echo $video_id; // NLqAF9hrVbY</code>

<code class="php">$url = 'http://youtu.be/NLqAF9hrVbY';
$oembed_url = sprintf('http://www.youtube.com/oembed?url=%s&amp;format=json', urlencode($url));
$oembed_response = json_decode(file_get_contents($oembed_url));
if ($oembed_response) {
    $video_id = $oembed_response->video_id;
}</code>