Parameter 'pattern' is serial of semitone numbers between two notes, 'transpose' is set interval from root c; if transpose = 0 then

scale.php

<?php
header('Content-Type: application/json');

$pattern = empty($_GET[pattern]) ? "2122122" : $_GET[pattern];
// transpose: positive(+) only and must be within 11
$transpose = empty($_GET[transpose]) ? 0 : $_GET[transpose];
$str_arr = str_split($pattern);

$names_common = array("", "C", "C+", "D", "E-", "E", "F", "F+", "G", "A-", "A", "B-", "B");
$names_sharp = array("", "C", "C+", "D", "D+", "E", "F", "F+", "G", "G+", "A", "A+", "B");

$sum = 1;
$output_arr = [];
$output_num = [];
$output_json = [];

// show first note
array_push($output_arr, $names_common[$sum + $transpose]);

foreach($str_arr as $e){
    $sum += $e;
    $disp_num = $transpose + $sum;
    if($disp_num > 12){
        array_push($output_arr, $names_common[$disp_num - 12]);
    } else {
        array_push($output_arr, $names_common[$disp_num]);
    }
    array_push($output_num, $disp_num);
}

$output_json = array("notesByName" => $output_arr, "notesBySemitone" => $output_num,
                     "root" => $names_common[$transpose + 1] , 
                     "name" => "example name", "pattern" => $pattern);

echo json_encode($output_json);

?>