code: public static function TRUNC($value = 0, $digits = 0)
      {
          $value = Functions::flattenSingleValue($value);
          $digits = Functions::flattenSingleValue($digits);
  
          // Validate parameters
          if ((!is_numeric($value)) || (!is_numeric($digits))) {
              return Functions::VALUE();
          }
          $digits = floor($digits);
  
          // Truncate
          $adjust = pow(10, $digits);
  
          if (($digits > 0) && (rtrim((int) ((abs($value) - abs((int) $value)) * $adjust), '0') < $adjust / 10)) {
              return $value;
          }
  
          return ((int) ($value * $adjust)) / $adjust;
      }
docs: TRUNC.
  
  Truncates value to the number of fractional digits by number_digits.
  
  @param float $value
  @param int $digits
  
  @return float Truncated value