nps-score.php

<?

// calculate nps score
// using formula promoters-detractors / number of respondents * 100

    /**
     * @param array
     * @return float
     */
    function output_real_nps($nps_array)
    {
        $detractors=0;
        $promoters=0;

        $arr_length=count($nps_array);

        for ($i=0;$i<$arr_length;$i++)
        {
            if (is_numeric($nps_array[$i]))
            {
                if ($nps_array[$i] <= 6 && $nps_array[$i] >= 0)
                    $detractors++;
                if ($nps_array[$i] >= 9 && $nps_array[$i] <= 10)
                    $promoters++;
            }
        }

        // div by 0 not allowed
        if ($arr_length>0)
            $nps_score=(($promoters-$detractors)/$arr_length)*100;
        else
            $nps_score='0';

        return round($nps_score,1);

    }
    
?>