php生成纯净url或class名

 * Formatting string
 *
 * @param string $string
 * @return string
 */
protected function ($string)
{
    $string = preg_replace('#[^0-9a-z]+#i', '-', $string);
    $string = strtolower($string);
    $string = trim($string, '-');
    return $string;
}