This is a big topic. I'll be brief.
This all depends upon your data structure. There are a couple of ways that
you can store information like this.
The classic (purist) method would be to have a table of the following type:
table_Tree
Node ID | Parent ID | Node Data
==========+===========+==========
1 | 0 | xxx
2 | 1 | xxx
3 | 1 | xxx
This describes a tree where node 1 is the top (parent id = 0) and has 2
children (nodes 2 and 3).
This approach can be used to describe any depth of tree with any number of
child nodes.
You then need to decide how to represent this in PHP. You could create a
node class that contains a collection of child nodes, a reference to the
parent node and the node data. You could then construct a physical
representation of your tree in PHP. You could then write some routines to
traverse your tree and count depth level of any particular node.
Alternatively, you could store the data in the db table in the same way in
PHP (as an array) and then write some routines to traverse your array. Both
approaches are valid and work. You would have to write the code to count the
depth of a node.
You could also store you information in the database as:
table_Tree
Node ID | Depth | Node Data
==========+===========+==========
1 | 0 | xxx
2 | 1 | xxx
3 | 1 | xxx
4 | 0 | xxx
Making the assumption that the rows are ordered correctly. By reading
row-by-row you can assume that if a following row is at a lower depth or the
same, then you are in the same branch of the tree. As soon as the depth is
at a higher level then you have traversed back up a branch. You can store
this representation directly in PHP in arrays and then write some routines
to render/handle your tree however you like. This approach will give you a
depth level directly, however, it's not as 'nice' as the first types of
trees as it relies upon order rather than strong relationships with child
nodes.
Your choice.
Hope that helps,
Neil
-----Original Message-----
From: E K L [mailto:[EMAIL PROTECTED]]
Sent: 23 March 2001 08:29
To: [EMAIL PROTECTED]
Subject: [PHP] Creating tree using table?
Hi all,
Currently, i'm trying to write a program which is related to tree
manipulation. Meaning that, i'll search the tree to get level or count how
many child exist for particular parent, for example.
Initially i planned to use table to represent all kind of datas that are
parent, left child and right child. However, i still face problem in
calculating the level of the tree. So, can any one gives me an idea on how
to manipulate the table so that i will be able to count the level?
Your prompt reply is much appreciated. Thanks....
E K
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