code: public function getCurrencySymbol($currencyCode = null)
      {
          $locale = $this->locale;
  
          if ($currencyCode !== null) {
              $locale .= '@currency=' . $currencyCode;
          }
  
          $formatter = new \NumberFormatter($locale, \NumberFormatter::CURRENCY);
          return $formatter->getSymbol(\NumberFormatter::CURRENCY_SYMBOL);
      }
docs: Returns a currency symbol
  
  @param string $currencyCode the 3-letter ISO 4217 currency code to get symbol for. If null,
  method will attempt using currency code from [[locale]].
  @return string