PHP - 防止 XSS（跨站脚本攻击）

<?PHP
/**
* @blog http://www.phpddt.com
* @param $string
* @param $low 安全别级低
*/
function clean_xss(&$string, $low = False)
{
   if (! is_array ( $string ))
   {
       $string = trim ( $string );
       $string = strip_tags ( $string );
       $string = htmlspecialchars ( $string );
       if ($low)
       {
           return True;
       }
       $string = str_replace ( array ('"', "\\", "'", "/", "..", "../", "./", "//" ), '', $string );
       $no = '/%0[0-8bcef]/';
       $string = preg_replace ( $no, '', $string );
       $no = '/%1[0-9a-f]/';
       $string = preg_replace ( $no, '', $string );
       $no = '/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]+/S';
       $string = preg_replace ( $no, '', $string );
       return True;
   }
   $keys = array_keys ( $string );
   foreach ( $keys as $key )
   {
       clean_xss ( $string [$key] );
   }
}
//just a test
$str = "<script>alert(document.cookie)</script>";
clean_xss($str); //如果你把这个注释掉，你就知道xss攻击的厉害了
echo $str;
?>