Array Problem

gaucho

Hello folks,
have a little problem with constructing a multidimensional array.
have a database that contains two tables, one is used as category index, the other one containes the category items.
The category index contains 3 fields: id, cat_id, cat_name.
the cat_id is a representation of the positions in the category tree and looks as follows:
Eg: 103025 means that the category is located at the 25th position level 3, which is a subcat. of the 3rd category at level 2, which is a subcat of the 1st category at level 1 of the tree.

OK, now the problem:
I retrieve the data from the index table which results in an array containing the cat_id and the cat_name. Then I use explode to split the cat_id, something like this:

$cat = explode("0", $row['cat_id']);

Keeping the example above the resulting array may look like this:
$cat( [0] => "1", [1] =>"3", [2] => "25");

Now I want to construct a multidimensional result Array may look like this:
$result([1] => Array( [dummy] => "dummy" //to initialize the structure
[cat_name] => "1stCat"
[cat_items] => Array([1] => ([item_name] => "1stItem", [description] =>"1stDecr"), [2] => (......))
[subcat] => Array([dummy] => "dummy", [1] => Array([subcat_name] => "subcat1", ....)
etc,etc, etc)
Hope this looks at least a little clear.
Well, and this construction is the problem. The construction of the partial arrays might not be the problem, but how should I merge the partial arrays correctly to where they belong in the result array to represent the tree.

Can anybody help me with this?

Thanks in advance.

Best regards

Gaucho

Weedpacket

I'm not entirely clear why you need the dummy elements; array() works well enough as an initialiser. But anyway.

So in your example $cat=array(1,3,25), you want the relevant stuff to go in the array referenced by
$result[1]['cat_items'][3]['subcat'][25]?
In general that would be $result[$cat[0]]['cat_items'][$cat[1]]['subcat'][$cat[2]].

This is how I'm reading your example:

$result([$cat[0]] => Array(
	['dummy'] => "dummy" //to initialize the structure
	['cat_name'] => "1stCat"
	['cat_items'] => Array(
		[$cat[1]] => Array(
			['item_name'] => "1stItem",
			['description'] =>"1stDecr"
		),
	['subcat'] => Array(
		['dummy'] => "dummy",
		[$cat[2]] => Array(
			['subcat_name'] => "subcat1", ....
		)
	)
)

gaucho

Not really,

"Movies" would represent level 1 in the tree, action, comedy and drama level 2, old ones and new ones level 3.
If you now have a film like "The Milkyway Drama" under the category "New Ones", the category ID would look like:
10302
In the index-table containing the categories you'll find something like this (for the tree above):
cat_id | cat_name
1 | Movies
1 | Music
1 | Games
101 | Action
102 | Comedy
103| Drama
10301| Old Ones
10302| New Ones

The table containing the "The Milkyway Drama" would have 10302 in the cat_id field and in the item field it would contain the name.
Retrieving the data from both tables should build an array like this (syntax is different now, to make it clearer):

$result[1][cat_name] = "Movies"
$result[1][subcats][1][cat_name] = "Action"
$result[1][subcats][2][cat_name] = "Comedy"
$result[1][subcats][3][cat_name] = "Drama"
$result[1][subcats][3][subcats][1][cat_name] = "Old Ones"
$result[1][subcats][3][subcats][2][cat_name] = "New Ones"
$result[1][subcats][3][subcats][2][items][1] = "The Milkyway Drama"
$result[1][subcats][3][subcats][2][items][2] = "Hell is Close"
$result[2][cat_name] = "Music"
$result[3][cat_name] = "Games"

Somehow better this way?
Like I said, the dynamic construction of such a multilevel array is my problem.
Anyone that could help me with this?
Thanks again

Greetz

Gaucho

gaucho

Hello again,
I was really trying hard to solve this problem, but had no luck yet.
Is there really nobody out there with an idea?

Greetings

Gaucho

xblue

Hi Gaucho,

I don't want to offend you by any means, but I think your data structure may cause some problems. Imagine

// value from database
// 103020 instead of 103025
$row['cat_id'])=103020; 
$cat = explode("0", $row['cat_id']); 
// you'd want this to be 20
echo $cat[2];

There are two common approaches to store tree structures with variable depth in a database, nested set model and storing the parent id with each child's record (there may be simpler ways for simpler tasks, e.g. if the depth will always be 3 or something, possibly more redundant or less efficient, but it always depends on your needs).

One more question: what exactly do you need the array for? if it is just for organizing html output, it might not really be necessary at all?

gaucho

Hello xblue,
you are absolutely right. I didn't think about this problem, I just stored some sample categories to the db, and didn't reach even 10 on each level, so I might have experienced some difficulties when reaching such a number. And don't worry, you don't offend me.
Well, what I need to do is to create something like a stock or warehouse db, it's for internal use. The depth must be absolutely variable.
The array is only needed for display, and I was already thinking about alternatives, I only always got stuck when trying to display a hierarchy tree, but now, after having read your comment, I think I have an idea. I remember my C++ times, and how it had to be done to build a tree, like a folder tree, the descendants always were set using the parent ID and the actual ID of the element, like you said.
Think I should try that.

Thanks

Greetings

Gaucho