pocketmine\utils\Utils::printable PHP Method

    public static function printable($str)
    {
        if (!is_string($str)) {
            return gettype($str);
        }
        return preg_replace('#([^\\x20-\\x7E])#', '.', $str);
    }

 public function __debugInfo()
 {
     $data = [];
     foreach ($this as $k => $v) {
         if ($k === "buffer") {
             $data[$k] = bin2hex($v);
         } elseif (is_string($v) or is_object($v) and method_exists($v, "__toString")) {
             $data[$k] = Utils::printable((string) $v);
         } else {
             $data[$k] = $v;
         }
     }
     return $data;
 }