Online PHP editor | refs for Cd9Pg

<?php // produces the expected result echo transpose("F#sus7/C#",3); function transpose($chord,$transpose) { // the chords $chords = array("C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"); $result = ""; // get root tone $root_arr = explode("/",$chord); $root = strtoupper($root_arr[0]); // the chord is the first character and a # if there is one $root = $root[0].((strpos($root, "#") !== false)?"#":""); // get any extra info $root_extra_info = str_replace("#","",substr($root_arr[0],1)); // assuming that extra info does not have any # // find the index on chords array $root_index = array_search($root,$chords); // transpose the values and modulo by 12 so we always point to existing indexes in our array $root_transpose_index = floor(($root_index + $transpose) % 12); if ($root_transpose_index < 0) { $root_transpose_index += 12; } $result.= $chords[$root_transpose_index].$root_extra_info; if(count($root_arr)>1) { // get the non root tone $non_root = $root_arr[1]; // the chord is the first character and a # if there is one $non_root = strtoupper($non_root[0]).((strpos($non_root, "#") !== false)?"#":""); // get any extra info $non_root_extra_info = str_replace("#","",substr($root_arr[1],1)); // assuming that extra info does not have any # // find the index on chords array $non_root_index = array_search($non_root,$chords); // transpose the values and modulo by 12 so we always point to existing indexes in our array $non_root_transpose_index = floor(($non_root_index + $transpose) % 12); if ($non_root_transpose_index < 0) { $non_root_transpose_index += 12; } $result.= "/".$chords[$non_root_transpose_index].$non_root_extra_info; } return $result; }