PHP get Vimeo id from url

function get_vimeoid( $url ) {
 $regex = '~
  # Match Vimeo link and embed code
  (?:<iframe [^>]*src=")?              # If iframe match up to first quote of src
  (?:                                  # Group vimeo url
    https?:\/\/                  # Either http or https
    (?:[\w]+\.)*                 # Optional subdomains
    vimeo\.com                   # Match vimeo.com
    (?:[\/\w:]*(?:\/videos)?)?   # Optional video sub directory this handles groups links also
    \/                           # Slash before Id
    ([0-9]+)                     # $1: VIDEO_ID is numeric
    [^\s]*                       # Not a space
  )                                    # End group
  "?                                   # Match end quote if part of src
  (?:[^>]*></iframe>)?                 # Match the end of the iframe
  (?:<p>.*</p>)?                       # Match any title information stuff
  ~ix';
   preg_match( $regex, $url, $matches );
   return $matches[1];
}