php - string replacement

[itvn85]

I am trying to do chord transposition in PHP the array of Chord values are as followed...\[code\]$chords1 = array('C','C#','D','D#','E','F','F#','G','G#','A','A#','B','C','Db','D','Eb','E','F','Gb','G','Ab','A','Bb','B','C');\[/code\]An example would be D6/F#. I want to match the array value and then transpose it by a given number position in the array. Here is what I have so far...\[code\]function splitChord($chord){ // The chord comes into the function preg_match_all("/C#|D#|F#|G#|A#|Db|Eb|Gb|Ab|Bb|C|D|E|F|G|A|B/", $chord, $notes); // match the item $notes = $notes[0]; $newArray = array(); foreach($notes as $note){ // for each found item as a note $note = switchNotes($note); // switch the not out array_push($newArray, $note); // and push it into the new array } $chord = str_replace($notes, $newArray, $chord); // then string replace the chord with the new notes available return($chord);}function switchNotes($note){ $chords1 = array('C','C#','D','D#','E','F','F#','G','G#','A','A#','B','C','Db','D','Eb','E','F','Gb','G','Ab','A','Bb','B','C'); $search = array_search($note, $chords1);////////////////Search the array position D=2 & F#=6 $note = $chords1[$search + 4];///////////////////////then make the new position add 4 = F# and A# return($note);}\[/code\]This works, except the problem is that if I use a split chord like (D6/F#) The chord is transposed to A#6/A#. It is replacing the first note (D) with an (F#) then, Both (F#'s) with an (A#). The question is... How can I keep this redundancy from happening. The desired output would be F#6/A#. Thank you for your help. If the solution is posted, I WILL mark it as answered.