code: public static function getCurrencyCode()
      {
          if (!empty(self::$currencyCode)) {
              return self::$currencyCode;
          }
          self::$currencyCode = '$';
          $localeconv = localeconv();
          if (!empty($localeconv['currency_symbol'])) {
              self::$currencyCode = $localeconv['currency_symbol'];
  
              return self::$currencyCode;
          }
          if (!empty($localeconv['int_curr_symbol'])) {
              self::$currencyCode = $localeconv['int_curr_symbol'];
  
              return self::$currencyCode;
          }
  
          return self::$currencyCode;
      }
docs: Get the currency code. If it has not yet been set explicitly, try to obtain the
  symbol information from locale.
  
  @return string