RegEx pattern to get the YouTube video ID from any YouTube URL

if (preg_match('/youtube\.com\/watch\?v=([^\&\?\/]+)/', $url, $id)) {
  $values = $id[1];
} else if (preg_match('/youtube\.com\/embed\/([^\&\?\/]+)/', $url, $id)) {
  $values = $id[1];
} else if (preg_match('/youtube\.com\/v\/([^\&\?\/]+)/', $url, $id)) {
  $values = $id[1];
} else if (preg_match('/youtu\.be\/([^\&\?\/]+)/', $url, $id)) {
  $values = $id[1];
}
else if (preg_match('/youtube\.com\/verify_age\?next_url=\/watch%3Fv%3D([^\&\?\/]+)/', $url, $id)) {
    $values = $id[1];
} else {   
// not an youtube video
}

This is what I use to extract the id from an youtube url. I think it works in all cases.

Note that at the end $values = id of the video

Instead of regex. I hightly recommend parse_url() and parse_str():

$url = "http://www.youtube.com/watch?v=8GqqjVXhfMU&feature=youtube_gdata_player";
parse_str(parse_url( $url, PHP_URL_QUERY ), $vars );
echo $vars['v'];    

Done

You could just use parse_url and parse_str:

$query_string = parse_url($url, PHP_URL_QUERY);
parse_str($query_string);
echo $v;

I have used the following patterns because YouTube has a youtube-nocookie.com domain too:

'@youtube(?:-nocookie)?\.com/watch[#\?].*?v=([^"\& ]+)@i',
'@youtube(?:-nocookie)?\.com/embed/([^"\&\? ]+)@i',
'@youtube(?:-nocookie)?\.com/v/([^"\&\? ]+)@i',
'@youtube(?:-nocookie)?\.com/\?v=([^"\& ]+)@i',
'@youtu\.be/([^"\&\? ]+)@i',
'@gdata\.youtube\.com/feeds/api/videos/([^"\&\? ]+)@i',

In your case it would only mean to extend the existing expressions with an optional (-nocookie) for the regular YouTube.com URL like so:

if (preg_match('/youtube(?:-nocookie)\.com\/watch\?v=([^\&\?\/]+)/', $url, $id)) {

If you change your proposed expression to NOT contain the final $, it should work like you intended. I added the -nocookie as well.

/**
 * get YouTube video ID from URL
 *
 * @param string $url
 * @return string YouTube video id or FALSE if none found. 
 */
function youtube_id_from_url($url) {
    $pattern = 
        '%^# Match any YouTube URL
        (?:https?://)?  # Optional scheme. Either http or https
        (?:www\.)?      # Optional www subdomain
        (?:             # Group host alternatives
          youtu\.be/    # Either youtu.be,
        |youtube(?:-nocookie)?\.com  # or youtube.com and youtube-nocookie
          (?:           # 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 (false !== $result) {
        return $matches[1];
    }
    return false;
}