multi level menu with codeigniter

I would recommend taking the HTML/formatting out of the model as a starting point. If you can create a library/helper with a method/function which simply takes an array and returns a formatted string for output, it should simplify the problem for you. Then your model can retrieve the data from the database and return a multidimensional array, e.g.

Code:

array(
    'menu 1',
    'menu 2',
    'menu 3' => array(
        'submenu 1',
    ),
    'menu 4' => array(
        'submenu 1',
    ),
)

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide