code: public function extractYouTubeId($varValue, Contao\DataContainer $dc)
  	{
  		if ($dc->activeRecord->youtube != $varValue)
  		{
  			$matches = array();
  
  			if (preg_match('%(?:youtube(?:-nocookie)?\.com/(?:[^/]+/.+/|(?:v|e(?:mbed)?)/|.*[?&]v=)|youtu\.be/)([^"&?/ ]{11})%i', $varValue, $matches))
  			{
  				$varValue = $matches[1];
  			}
  		}
  
  		return $varValue;
  	}
docs: Extract the YouTube ID from an URL
  
  @param mixed                $varValue
  @param Contao\DataContainer $dc
  
  @return mixed