I am trying to turn flat mysql rows into a tree structure.
$categories = array(
array(
'id' => '1',
'name' => 'root',
'parent' => '0',
),
array(
'id' => '2',
'name' => 'first',
'parent' => '1',
),
array(
'id' => '3',
'name' => 'first',
'parent' => '1',
),
array(
'id' => '4',
'name' => 'second',
'parent' => '3',
),
);
I am initializing all the first level nodes first then calling build_tree on each node.
$hierarchy = array();
// loop through and get each root node
foreach($categories as $key => $category) {
if ($category['parent'] == 0) {
// initialize this root
$hierarchy[$category['id']] = $category;
$hierarchy[$category['id']]['children'] = array();
// remove this from categories
unset($categories[$key]);
$this->build_tree($hierarchy[$category['id']], $categories);
}
}
return $hierarchy;
}
function build_tree(&$node, &$categories) {
foreach ($categories as $key => $category) {
// check if this node is the parent
if ($node['id'] === $category['parent']) {
$node['children'][$category['id']] = $category;
$node['children'][$category['id']]['children'] = array();
unset($categories[$key]);
$this->build_tree($category, $categories);
}
}
}
THis is only returning the first and second levels of the tree.
array
1 =>
array
'id' => string '1' (length=1)
'name' => string 'root' (length=4)
'parent' => string '0' (length=1)
'children' =>
array
2 =>
array
'id' => string '2' (length=1)
'name' => string 'first' (length=5)
'parent' => string '1' (length=1)
'children' =>
array
empty
3 =>
array
'id' => string '3' (length=1)
'name' => string 'first' (length=5)
'parent' => string '1' (length=1)
'children' =>
array
empty
Inside of build_tree when it reaches id=2 it is creating children successfully. (finding that there is one child of id=2 and appending it to 'children' correctly)
It is just not saving it! Can anyone see what I am doing wrong?? When I var_dump hierarchy it is just the first and second level never the third even though the third is being created successfully in build_tree. Any help would be very greatly appreciated. Ty.
For the sake of performance, it is usually a good practice to consider non-recursive solutions before recursive ones. I put together a bit of code that hopefully can help you with your category tree problem:
$dbh->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
$sth = $dbh->prepare('SELECT * FROM categories');
$sth->execute();
$categories = $sth->fetchAll();
function buildCategoryTree(&$categories)
{
$tree = array(0=>array('children'=>array()));
foreach($categories as &$c)
{
$tree[$c['id']] = &$c;
}
foreach($categories as &$c)
{
$parent_id = $c['parent'] ?: 0;
if(!isset($tree[$parent_id])) $tree[$parent_id]['children'] = array();
$tree[$parent_id]['children'][] = &$c;
}
return $tree[0]['children'];
}
$tree = buildCategoryTree($categories);
If you had the following in the database:
mysql> SELECT * FROM categories;
+----+------+--------+
| id | name | parent |
+----+------+--------+
| 1 | A | 0 |
| 2 | B | 0 |
| 3 | C | 0 |
| 4 | A1 | 1 |
| 5 | A2 | 1 |
| 6 | B1 | 2 |
| 7 | B2 | 2 |
| 8 | C1 | 3 |
| 9 | A3 | 1 |
| 10 | B2i | 7 |
| 11 | A1ii | 4 |
| 12 | A1i | 4 |
+----+------+--------+
then the code would produce $tree as:
Array
(
[0] => Array
(
[id] => 1
[name] => A
[parent] => 0
[children] => Array
(
[0] => Array
(
[id] => 4
[name] => A1
[parent] => 1
[children] => Array
(
[0] => Array
(
[id] => 11
[name] => A1ii
[parent] => 4
)
[1] => Array
(
[id] => 12
[name] => A1i
[parent] => 4
)
)
)
[1] => Array
(
[id] => 5
[name] => A2
[parent] => 1
)
[2] => Array
(
[id] => 9
[name] => A3
[parent] => 1
)
)
)
[1] => Array
(
[id] => 2
[name] => B
[parent] => 0
[children] => Array
(
[0] => Array
(
[id] => 6
[name] => B1
[parent] => 2
)
[1] => Array
(
[id] => 7
[name] => B2
[parent] => 2
[children] => Array
(
[0] => Array
(
[id] => 10
[name] => B2i
[parent] => 7
)
)
)
)
)
[2] => Array
(
[id] => 3
[name] => C
[parent] => 0
[children] => Array
(
[0] => Array
(
[id] => 8
[name] => C1
[parent] => 3
)
)
)
)