How can I add my Bootstrap classes to a custom menu?

Question

How can I add different Bootstrap menus to menu_tree_output()?

I know this is a very common question asked by a number of people earlier. I have found tons of answers, but none of them are working for me. However, I have tried a number snippets and here is the latest piece of code I am working on to get all menus and sub-menus.

<?php 
  $menuTree = menu_tree_all_data('main-menu');
  $menu_tree_array = menu_tree_output($menuTree);
  print render($menu_tree_array);
?>

It works and prints all the submenus, however, It adds the same "menu" class to all parent ul. Rather I would like add sub-menu classes like the below output:

<div class="navbar-collapse collapse">
  <div class="menu-top-menu-container">
    <ul id="menu-top-menu" class="nav navbar-nav">
      <li>
        <a href="http://example.com/">Home</a>
      </li>
      <li>
        <a href="http://example.com/biography/">Biography</a>
      </li>
      <li>
        <a href="#">Services</a>
        <ul class="sub-menu"> <!-- Like this. -->
          <li></li>
          <li></li>
        </ul>
      </li>
    </ul>
  </div>
</div>

Answer 1

What you want is theme_menu_link(). See the example here.

Answer 2

You can always use the Menu attributes module.