If the root user doesn't have a `position` value (i.e., no `'left'` or `'right'` position assigned), you'll need to handle that separately in the logic. For the root user (whose `placement` is `NULL` or `''`), the `position` condition will not be satisfied because the root node does not have a position.
### Solution:
1. **Identify the Root User**: The root user is the one whose `placement` is `NULL` or an empty string (`''`).
2. **Skip the `position` check for the Root User**: For the root user, you don't need to check for `position`. Instead, just place them as the root, and then handle their children by checking their positions (`left` or `right`).
### Updated Code:
```php
function buildTree($users, $parentId = null) {
$branch = array('left' => array(), 'right' => array());
foreach ($users as $user) {
// Root node check: If the placement is NULL or blank, and no position is required for root
if ($parentId === null && $user['placement'] == '') {
// This is the root user, no left or right check
$branch = array(
'userid' => $user['userid'],
'children' => buildTree($users, $user['userid']) // Recursively build the tree for children
);
}
// For non-root users, check placement and position (left or right)
elseif ($user['placement'] == $parentId) {
if ($user['position'] == 'left') {
$branch['left'][] = array(
'userid' => $user['userid'],
'children' => buildTree($users, $user['userid']) // Recursively call for left children
);
} elseif ($user['position'] == 'right') {
$branch['right'][] = array(
'userid' => $user['userid'],
'children' => buildTree($users, $user['userid']) // Recursively call for right children
);
}
}
}
return $branch;
}
```
### Key Changes:
1. **Root Node Handling**:
If the `parentId` is `null` and the `placement` is empty (`''`), then this is the root node. It will not have a `position`, so you handle it separately.
```php
if ($parentId === null && $user['placement'] == '') {
$branch = array(
'userid' => $user['userid'],
'children' => buildTree($users, $user['userid']) // Continue building tree for children
);
}
```
2. **Non-root Nodes**:
For users with a `placement` (i.e., non-root users), you check their `position` (`left` or `right`) and place them accordingly in the tree.
```php
elseif ($user['placement'] == $parentId) {
if ($user['position'] == 'left') {
$branch['left'][] = array(
'userid' => $user['userid'],
'children' => buildTree($users, $user['userid']) // Recursively build for left children
);
} elseif ($user['position'] == 'right') {
$branch['right'][] = array(
'userid' => $user['userid'],
'children' => buildTree($users, $user['userid']) // Recursively build for right children
);
}
}
```
### Display Function:
Once the tree is built, you can display it as follows:
```php
function displayTree($tree) {
if (empty($tree)) {
return;
}
// Display root node
echo '<div class="parent-node">' . $tree['userid'] . '</div>';
// Display left and right children
echo '<div class="tree-container">';
// Left side
if (!empty($tree['children']['left'])) {
echo '<div class="left-branch">';
echo '<ul>';
foreach ($tree['children']['left'] as $node) {
echo '<li>' . $node['userid'];
displayTree($node['children']); // Recursively display children
echo '</li>';
}
echo '</ul>';
echo '</div>';
}
// Right side
if (!empty($tree['children']['right'])) {
echo '<div class="right-branch">';
echo '<ul>';
foreach ($tree['children']['right'] as $node) {
echo '<li>' . $node['userid'];
displayTree($node['children']); // Recursively display children
echo '</li>';
}
echo '</ul>';
echo '</div>';
}
echo '</div>';
}
```
### How This Works:
- The root user will not have a `position`, so the function handles this separately when `parentId` is `null` and `placement` is `''`.
- For all other users, the function checks whether they are in the `left` or `right` position of their parent, and the tree is built accordingly.
### Example:
If you have the following structure in your database:
| userid | placement | position |
|--------|-----------|----------|
| rp1 | | |
| rp2 | rp1 | left |
| rp3 | rp1 | right |
| rp4 | rp2 | left |
| rp5 | rp3 | right |
- `rp1` is the root, as its `placement` is blank.
- `rp2` is in the left position of `rp1`.
- `rp3` is in the right position of `rp1`.
- `rp4` is in the left position of `rp2`.
- `rp5` is in the right position of `rp3`.
The tree would display with `rp1` as the root, with `rp2` and `rp3` as its left and right children, respectively, and so on.
Let me know if this resolves your issue!
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