Hierarchical recursion menu with PHP/MySQL

Question

This should (hopefully) be a pretty easy question for some of you to answer.

I have a working Recursive menu from a mySQL database, now my main problem is:

What is the best way to create the URL? I would prefer to bring in the title of each row like /eggs/milk/bacon/. Eggs being level 0 like: eggs-0, milk-1, bacon-2. Any ideas on how to dynamicly output this?

I am pretty much going for what "cletus" said a few comments down on this question: PHP/MySQL - building a nav menu hierarchy

But I need a bit more explanation on how to do it.

Answer 1

Well, if you want a hierarchy, be best method I know of is called "Modified Preorder Tree Traversal" that is described in great detail in this Sitepoint article , starts about halfway down.

The main difference from what Guss suggested is that it's a bit more performant and a lot easier to only fetch the part of the tree you're looking for.

Answer 2

Unless you plan to modify your menu tree often, pre-storing the required hierarchical URL for each menu item is probably the easiest (for run-time resolution that is).

If you expect the tree to be modified often enough, lets say - through a web interface, then it would be easier to generate the paths every time you read the menu, something like this:

 id | name   | parent
----+--------+-------
 0  | eggs   | NULL
 1  | milk   | 0
 2  | bacon  | 1
 3  | tomato | 0
 4  | lettuce| 1

foreach (query("SELECT * FROM menu ORDER BY parent ASC") as $row) {
  $menuitem = array_merge(array(), $row);
  $menuLookup[$menuitem['id']] &= $menuitem;
  if ($menuitem['parent'] == null) {
    $menuitem['path'] = "/" . $menuitem['name'];
    $menu[] &= $menuitem[];
  } else {
    $parent &= $menuLookup[$menuitem['parent']];
    $menuitem['path'] = $parent['path'] . "/" . $menuitem['name'];
    $parent['menu'][] &= $menuitem;
  }
}

I haven't debugged this code, only tested it for correctness ;-)

Answer 3

我在groovy写了一些东西： http ： //blog.srvme.de/2009/11/29/reading-a-reflexive-association-in-a-recursive-way-for-grails-and-groovy/