code: private static function encodeUTF16($string, $compressed = false)
      {
          if ($compressed) {
              $string = self::uncompressByteString($string);
          }
  
          return StringHelper::convertEncoding($string, 'UTF-8', 'UTF-16LE');
      }
docs: Get UTF-8 string from (compressed or uncompressed) UTF-16 string.
  
  @param string $string
  @param bool $compressed
  
  @return string