code: public static function getFolderHash($strPath)
  	{
  		$strPath = str_replace(array('\\', '%', '_'), array('\\\\', '\\%', '\\_'), $strPath);
  		$arrHash = array();
  
  		$objChildren = Database::getInstance()
  			->prepare("SELECT hash, name FROM tl_files WHERE path LIKE ? AND path NOT LIKE ? ORDER BY name")
  			->execute($strPath.'/%', $strPath.'/%/%')
  		;
  
  		if ($objChildren !== null)
  		{
  			while ($objChildren->next())
  			{
  				$arrHash[] = $objChildren->hash . $objChildren->name;
  			}
  		}
  
  		return md5(implode("\0", $arrHash));
  	}
docs: Get the folder hash from the databse by combining the hashes of all children
  
  @param string $strPath The relative path
  
  @return string MD5 hash