code: public function fwhm()
      {
          $float_fwhm = 2 * sqrt(2 * log(2)) * $this->float_sigma;
  
          if ($this->int_precision) {
              return round($float_fwhm, $this->int_precision);
          }
  
          return $float_fwhm;
      }
docs: Gets the full width at half maximum.
  
  @see NormalDistribution::precision()
  @access public
  @return float