PHP Chord Transposer

<?php
//require_once("dompdf/dompdf_config.inc.php");

class Transposer
{
    private $type = 'sharps';
    private $notes = array(
        'scale' => array(
          'C'  => 1,
          'C#' => 2,
          'Db' => 2,
          'D'  => 3,
          'D#' => 4,
          'Eb' => 4,
          'E'  => 5,
          'Fb' => 5,
          'F'  => 6,
          'F#' => 7,
          'Gb' => 7,
          'G'  => 8,
          'G#' => 9,
          'Ab' => 9,
          'A'  => 10,
          'A#' => 11,
          'Bb' => 11,
          'B'  => 12,
          'Cb' => 12
        ),
      'flats'  => array(1 => 'C', 'Db', 'D', 'Eb', 'E', 'F', 'Gb', 'G', 'Ab', 'A', 'Bb', 'B'),
      'sharps' => array(1 => 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B')
   );
   private $search = '`([ABCDEFG][b#]?(?=\s(?![a-zH-Z])|(?=(2|5|6|7|9|11|13|6\/9|7\-5|7\-9|7\#5|7\#9|7‌\+5|7\+9|7b5|7b9|7sus2|7sus4|add2|add4|add9|aug|dim|dim7|m\|maj7|m6|m7|m7b5|m9|m1‌1|m13|maj7|maj9|maj11|maj13|mb5|m|sus|sus2|sus4|\))(?=(\s|\/)))|(?=(\/|\.|-|\(|\)))))`';
   private $search2 = '`([ABCDEFG][b#]?[m]?[\(]?(2|5|6|7|9|11|13|6\/9|7\-5|7\-9|7\#5|7\#9|7\+5|7\+9|7b5|7b9|7sus2|7sus4|add2|add4|add9|aug|dim|dim7|m\|maj7|m6|m7|m7b5|m9|m11|m13|maj7|maj9|maj11|maj13|mb5|m|sus|sus2|sus4)?(\))?)(?=\s|\.|\)|-|\/)`';
   private $song;
   private $steps;
   private $formattedChords = array();
   private $replacementChords = array();

    public function __construct($song_,$steps_) {
        $this->song = $song_;
        $this->steps = $steps_;
        preg_match_all($this->search, $this->song, $song_chords);
        //print_r($u = array_unique($song_chords[0]))."\n";
        $u = array_unique($song_chords[0]);
        foreach ($u as $chord){
            if (strlen($chord) > 1  && ($chord{1} == "b" || $chord{1} == "#"))
                array_push($this->formattedChords,substr($chord,0, 2));
            else
                array_push($this->formattedChords,substr($chord,0, 1));
        }
        //print_r($this->formattedChords)."\n";
        $this->song = preg_replace($this->search,'|$1|',$this->song);
        foreach($this->formattedChords as $note) {
            $len = strlen($note);
            $len = $len - 1;
            switch ($note{$len}) {
                case "b":
                    $this->transpose($note,'flats',$this->steps);
                    break;
                case "#":
                    $this->transpose($note,'sharps',$this->steps);
                    break;
                default:
                    $this->transpose($note,'sharps',$this->steps);
            }
        }
        foreach($this->formattedChords as &$note){
            $note = "/\|".$note."\|/";
        }
        $this->song = preg_replace($this->formattedChords, $this->replacementChords, $this->song);
         $html= preg_replace($this->search2,'<b>$1</b>',$this->song);
         $old = array("<pre>", "\r", "\n", "</pre>");
          $new = array("<pre><span>", "", "</span>\n<span>", "</span></pre>");


         $html ='<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><html><body><pre>'.$html.'</pre></body></html>';

$html = str_replace($old, $new, $html);
echo $html = str_replace("<span></span>","<span> </span>",$html);
//$dompdf = new DOMPDF();
//$dompdf->load_html($html);
//$dompdf->render();
//strlen($html);
//$dompdf->stream("sample.pdf");
    }

    public function transpose($note,$types,$steps){

        if(isset($this->notes['scale'][$note]))
        {
            $ix = $this->notes['scale'][$note];
        }
        else
        {
            user_error("Invalid note '$note'");
            return false;
        }
        $ixNew = $ix + $steps;
        if(!isset($this->notes[$types][$ixNew])) {
            $ixNew += ($ixNew > 0) ? -12 : 12;
            if(!isset($this->notes[$types][$ixNew]))
                throw new Exception("My math skills suck! $note : $steps : $ix : $ixNew");
        }
        array_push($this->replacementChords,$this->notes[$types][$ixNew]);
        //echo "/|".$note."|/";
    }
}


      //$new_song = preg_replace($u, $new, $song);

        //echo $clean = str_replace('|', '', $new_song);

$song = "
God is able - Hillsong
       B
God is able
        F#
He will never fail
Abm E
He is almighty God
             B
Greater than all we need
             F#
Greater than all we have
Abm E F#
He has done great things

Chorus:
       B
Lifted up
             F#
Defeated the grave
          Abm
Raised to life
           E
Our God is able
       B/D#
In His name
       F#
We overcome
        Abm
For the Lord
    F# E
Our God is able

Verse 2:
God is with us
God is on our side
He will make a way
Far above all we know
Far above all we hope
He has done great things

Bridge:
       B
God is with us
        F#
He will go before
        Abm
He will never leave us
        E
He will never leave us

       B/D#
God is for us
       F#
He has open arms
        Abm F#
He will never fail us
               E
He will never fail us

";
$test = new Transposer($song,2);


?>