Alphabetical Pagination / Sort by in CakePHP

function index($filter = null) {
	$this->SttwTrack->recursive = 0;
 
	$this->set('filter', $filter);
 
     // query all distinct first letters used in names
     $letters = $this->SttwTrack->query('SELECT DISTINCT SUBSTRING(`title`, 1, 1) FROM `sttw_tracks` ORDER BY `title`');
 
     $links = array();
     // push all letters into a non-nested array
     foreach ($letters as $row) {
          array_push($links, current($row[0]));
     }
 
     $this->set('links', $links);
 
     $this->paginate['SttwTrack'] = array(
     'limit' => 10,
     'order' => array(
          'SttwTrack.title' => 'asc'
      )
	);
 
	$data = $this->paginate('SttwTrack',
	     array(
	          'SttwTrack.title LIKE' => $filter .'%'
	     )
	);
 
	$this->set('data', $data);
	$this->set('filter', $filter);
	$this->set('sttwTracks', $this->paginate());
}

// set url arguements
$paginator->options(array('url' =>  array($filter)));
 
// render the previous link
echo $paginator->prev('prev',null,null,null);
 
// set up your alphabet
$alpha = range('A','Z');
echo "<ul class=\"sortby\">";
for ($i=0; $i < count($alpha); $i++) {
	echo "<li>";
	// if current letter is not in the links array, do not make it clickable
	if(!in_array($alpha[$i], $links)) {
		echo"<span class='nolink'>" . $alpha[$i] . "</span>";
	} else {
		if ($alpha[$i] == $filter) {
			// if the current letter matches the filter, give it a selected style
			echo $html->link($alpha[$i], array('controller' => strtolower($this->params['controller']), 'action' => 'index', $alpha[$i]), array('class' => 'link_selected')) . "";
		} else {
			echo $html->link($alpha[$i], array('controller' => strtolower($this->params['controller']), 'action' => 'index', $alpha[$i]), array('class'=>'link')) . "";
		}
	}
	echo "</li>";
}
echo "</ul>";
// render the 'next' link
echo $paginator->next('next', null, null, null);