apply styles to php code

I using this block of code to call up category items in an application...

$categories = '';
$selected = 0;
$currentlevel = 1;
for ($i=0; $i<sizeof($this->Categories); $i++){  

  if ($this->Categories[$i]->level > ($currentlevel)){
$categories .= '<ul>';
  }
elseif ($this->Categories[$i]->level == ($currentlevel)){
$categories .= '</li>';
}

  for ($k= ($currentlevel - $this->Categories[$i]->level);$k>0;$k--){
   $categories .= '</ul></li>';

  }

  $categories .= '<li><a href="'.$this->Categories[$i]->url.'">'.$this->Categories[$i]->title.'</a>'."\n";

$currentlevel = $this->Categories[$i]->level;
}

PHP:

I'd like it to display in the format below

<li><a class="MenuBarItemSubmenu" href="#">Item 1</a>
                    <ul>
                      <li><a href="#">Item 1.2</a></li>
                      <li><a href="#">Item 1.3</a></li>
                    </ul>
                </li>
                <li><a href="#" class="MenuBarItemSubmenu">Untitled Item</a>
                  <ul>
                    <li><a href="#">Untitled Item</a></li>
                    <li><a href="#">Untitled Item</a></li>
                  </ul>
                 </li>

HTML:

any help will be appreciated.
thanks!