Algorithm to Save Items with Parent-Child Relationship to Database - recursion

Question

I need help designing the logic of an app that I am working on.
The application should enable users to create mindmaps and save them to a mysql database for later editing.
Each mindmap is made up of inter-related nodes, meaning a node should have a parent node and the id of the mindmap to which it belongs.
I am stuck here. How can I save the nodes to the database and be able to query and rebuild the mindmap tree from the query results.
Root
Child1
Child2
GrandChild1
GreatGrandChild1
GreatGrandChild1
Child3
GrandChild2
I need an algorithm, that can save the nodes and also be able to figure out the relationships/order of items similar to the Tree that I have given. This is very much like how menus are saved and retrieved in Wordpress but I can't find the right logic to do this.
I know there are really great people here. Please help.

Answer 1

This is very easy in a 3 column table.
Column-1: id, Column-2: name, Column-3: parent_id
for example, the data would be like this:
1 ROOT NULL
2 Child1 1
3 Child2 1
... and so on..

Answer 2

I finally found a solution. Here's my full code.
require_once('config.php');//db conn
$connect = mysql_connect(DB_HOST, DB_USER, DB_PASS);
mysql_select_db(DB_NAME);
$nav_query = MYSQL_QUERY("SELECT * FROM `nodes` ORDER BY `id`");
$tree = ""; // Clear the directory tree
$depth = 1; // Child level depth.
$top_level_on = 1; // What top-level category are we on?
$exclude = ARRAY(); // Define the exclusion array
ARRAY_PUSH($exclude, 0); // Put a starting value in it
WHILE ( $nav_row = MYSQL_FETCH_ARRAY($nav_query) )
{
$goOn = 1; // Resets variable to allow us to continue building out the tree.
FOR($x = 0; $x < COUNT($exclude); $x++ ) // Check to see if the new item has been used
{
IF ( $exclude[$x] == $nav_row['id'] )
{
$goOn = 0;
BREAK; // Stop looking b/c we already found that it's in the exclusion list and we can't continue to process this node
}
}
IF ( $goOn == 1 )
{
$tree .= $nav_row['name'] . "<br>"; // Process the main tree node
ARRAY_PUSH($exclude, $nav_row['id']); // Add to the exclusion list
IF ( $nav_row['id'] < 6 )
{ $top_level_on = $nav_row['id']; }
$tree .= build_child($nav_row['id']); // Start the recursive function of building the child tree
}
}
FUNCTION build_child($oldID) // Recursive function to get all of the children...unlimited depth
{
$tempTree='<ul>';
GLOBAL $exclude, $depth; // Refer to the global array defined at the top of this script
$child_query = MYSQL_QUERY("SELECT * FROM `nodes` WHERE parent_id=" . $oldID);
WHILE ( $child = MYSQL_FETCH_ARRAY($child_query) )
{
IF ( $child['id'] != $child['parent_id'] )
{
FOR ( $c=0;$c<$depth;$c++ ) // Indent over so that there is distinction between levels
{ $tempTree .= " "; }
$tempTree .= "<li>" . $child['name'] . "</li>";
$depth++; // Incriment depth b/c we're building this child's child tree (complicated yet???)
$tempTree .= build_child($child['id']); // Add to the temporary local tree
$depth--; // Decrement depth b/c we're done building the child's child tree.
ARRAY_PUSH($exclude, $child['id']); // Add the item to the exclusion list
}
}
RETURN $tempTree.'</ul>'; // Return the entire child tree
}
ECHO $tree;
?>
This is based on the piece of code found here http://psoug.org/snippet/PHP-Recursive-function-to-generate-a-parentchild-tree_338.html I hope this helps someone as well