public function temperature($input = 0)
    {
        $input = (float) $input;

        if ($this->input == 'si' && $this->output == 'si') {
            $this->displayFormat = 'C';
            $output              = (float) $input;
        } elseif ($this->input == 'si' && $this->output == 'uscs') {
            $this->displayFormat = 'F';
            $output              = (float) ((($input / 5) * 9) + 32);
        } elseif ($this->input == 'uscs' && $this->output == 'si') {
            $this->displayFormat = 'C';
            $output              = (float) ((($input - 32) / 9) * 5);
        } elseif ($this->input == 'uscs' && $this->output == 'uscs') {
            $this->displayFormat = 'F';
            $output              = (float) $input;
        }

        return (float) $output;
    }