PHP/MySQL - building a nav menu hierarchy

Question

So the final menu will look something like this:

Item B
    Item B-1
        Item B-1-2
        Item B-1-1
Item A
    SubItem A-1
    SubItem A-2
Item C
         


        

Answer 1

Hierarchical data is somewhat annoying in a relationsal database (excluding Oracle, which has operators in START WITH/CONNECT BY to deal with this). There are basically two models: adjacency list and nested sets.

You've chosen adjacency sets, which is what I typically do too. It's far easier to change than the nested set model, although the nested set model can be retrieved in the correct order in a single query. Adjacency lists can't be. You'll need to build an intermediate data structure (tree) and then convert that into a list.

What I would do (and have done recently in fact) is:

• select the entire menu contents in one query ordered by parent ID;
• Build a tree of the menu structure using associative arrays or classes/objects;
• Walk that tree to create nested unordered lists; and
• Use a jQuery plug-in like Superfish to turn that list into a menu.

You build something like this:

$menu = array(
  array(
    'name' => 'Home',
    'url' => '/home',
  ),
  array(
    'name' => 'Account',
    'url' => '/account',
    'children' => array(
      'name' => 'Profile',
      'url' => '/account/profile',
    ),
  ),
  // etc
);

and convert it into this:

;
  
Home
  
Account Services
    

      
Profile
...

The PHP for generating the menu array from is reasonably straightforward but a bit finnicky to solve. You use a recursive tree-walking function that builds the HTML nested list markup but will leave it's implementation as an exercise for the reader. :)