问题
I\'ve looked around the internet and haven\'t quite found what I\'m looking for. I have a flat array with each element containing an \'id\' and a \'parent_id\'. Each element will only have ONE parent, but may have multiple children. If the parent_id = 0, it is considered a root level item. I\'m trying to get my flat array into a tree. The other samples I have found only only copy the element to the parent, but the original still exists.
EDIT
Each element of the starting array is read from a separate XML file. The file itself will have \'0\' as the value for parent_id if it doesn\'t have a parent. The keys are actually strings.
I\'m sorry for the confusion earlier. Hopefully this is more clear:
/EDIT
My starting array:
Array
(
[_319_] => Array
(
[id] => 0
[parent_id] => 0
)
[_320_] => Array
(
[id] => _320_
[parent_id] => 0
)
[_321_] => Array
(
[id] => _321_
[parent_id] => _320_
)
[_322_] => Array
(
[id] => _322_
[parent_id] => _321_
)
[_323_] => Array
(
[id] => _323_
[parent_id] => 0
)
[_324_] => Array
(
[id] => _324_
[parent_id] => _323_
)
[_325_] => Array
(
[id] => _325_
[parent_id] => _320_
)
)
The resulting array after the tree is made:
Array
(
[_319_] => Array
(
[id] => _319_
[parent_id] => 0
)
[_320_] => Array
(
[id] => _320_
[parent_id] => 0
[children] => Array
(
[_321_] => Array
(
[id] => _321_
[parent_id] => _320_
[children] => Array
(
[_322_] => Array
(
[id] => _322_
[parent_id] => _321_
)
)
)
[_325_] => Array
(
[id] => _325_
[parent_id] => _320_
)
)
[_323_] => Array
(
[id] => _323_
[parent_id] => 0
[children] => Array
(
[_324_] => Array
(
[id] => _324_
[parent_id] => _323_
)
)
)
Any help / guidance is greatly appreciated!
Some code I have so far:
function buildTree(array &$elements, $parentId = 0) {
$branch = array();
foreach ($elements as $element) {
if ($element[\'parent_id\'] == $parentId) {
$children = $this->buildTree($elements, $element[\'id\']);
if ($children) {
$element[\'children\'] = $children;
}
$branch[] = $element;
}
}
return $branch;
}
回答1:
You forgot the unset() in there bro.
function buildTree(array &$elements, $parentId = 0) {
$branch = array();
foreach ($elements as $element) {
if ($element['parent_id'] == $parentId) {
$children = buildTree($elements, $element['id']);
if ($children) {
$element['children'] = $children;
}
$branch[$element['id']] = $element;
unset($elements[$element['id']]);
}
}
return $branch;
}
回答2:
The solution by ImmortalFirefly is working, however, as mrded points out, it doesn't save first parents without children. I've edited the function to fix this issue:
function buildTree(array &$elements, $parentId = 0) {
$branch = array();
foreach ($elements as &$element) {
if ($element['parent_id'] == $parentId) {
$children = buildTree($elements, $element['id']);
if ($children) {
$element['children'] = $children;
}
$branch[$element['id']] = $element;
unset($element);
}
}
return $branch;
}
回答3:
This works for me:
$index=array();
$tree=array();
foreach ($ori as $key=>$var) {
$var=array_shift($ori);
if ($var['id']==0) $var['id']=$key;
if ((string)$var['parent_id']==='0') {
$tree[$key]=$var;
$index[$key]=&$tree[$key];
} else if (isset($index[$var['parent_id']])) {
if (!isset($index[$var['parent_id']]['children'])) $index[$var['parent_id']]['children']=array();
$index[$var['parent_id']]['children'][$key]=$var;
$index[$key]=&$index[$var['parent_id']]['children'][$key];
} else {
array_push($ori,$var);
}
}
unset($index);
print_r($tree);
回答4:
I can see the logic, save for this in the result:
Array
(
[0] => Array
(
[id] => 0
[parent_id] => 0
)
[1] => Array
(
[id] => 1
[parent_id] => 0
)
IMHO, is parent_id = o, shouldn't [1] be a child of [0] here?
Anyway, references to the rescue:
$tree = array();
foreach($inputarray as $item){
if(!isset($tree[$item['id']])) $tree[$item['id']] = array();
$tree[$item['id']] = array_merge($tree[$item['id']],$item);
if(!isset($tree[$item['parent_id']])) $tree[$item['parent_id']] = array();
if(!isset($tree[$item['parent_id']]['children'])) $tree[$item['parent_id']]['children'] = array();
$tree[$item['parent_id']]['children'][] = &$tree[$item['id']];
}
$result = $tree[0]['children'];
unset($tree);
print_r($result);
Because you have abused 0 as both a 'magic' number as root, and an existing id, we now have recursion in the id=0 branch. Adding if($item['parent_id']!=$item['id']) before $tree[$item['parent_id']]['children'][] = &$tree[$item['id']]; could prevent that, but it isn't pretty.
回答5:
It's possible to construct the source array slightly different you can use this function(parent_id,id,title):
$q = mysql_query("SELECT id, parent_id, name FROM categories");
while ($r = mysql_fetch_row($q)) {
$names[$r[0]] = $r[2];
$children[$r[0]][] = $r[1];
}
function render_select($root=0, $level=-1) {
global $names, $children;
if ($root != 0)
echo '<option>' . strrep(' ', $level) . $names[$root] . '</option>';
foreach ($children[$root] as $child)
render_select($child, $level+1);
}
echo '<select>';
render_select();
echo '</select>';
- More efficient hierarchy system
回答6:
Though this is an old question, I'm gonna post my answer here:
/* assuming top level pid = 0 */
$rows = array (
array ( 'id' => 1, 'pid' => 0 ),
/* ... */
);
/* make id become array key */
$rows = array_column ( $rows, null, 'id' );
foreach ( $rows as $key => $val ) {
if ( $val ['pid'] ) {
if ( isset ( $rows [$val ['pid']] )) {
$rows [$val ['pid']]['children'][] = &$rows [$key];
}
}
}
foreach ( $rows as $key => $val ) {
if ( $val ['pid'] ) unset ( $rows [$key] );
}
array_column is PHP 5.5 but you can make your own easily.
回答7:
You want to be looking at storing and loading hierarchical data in MySQL as I this should solve a few problems. I'm assuming that the first array represents data taken directly from the database?
It looks like you're trying to use the adjacency model to organize your data into the hierarchy structure. There are also other ways to achieve this using nesting. If you are not taking this data from a database then this may not be as useful.
This link should help you out: http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/
回答8:
SteveEdson's code works fine, except in the case where the parent of an element does not exist in the original data structure. Here's my fix for that (however, it removes "parent_id" from elements, which may or may not be acceptable):
function buildTree(array &$elements, $parentId = 0)
{
$branch = array();
foreach ($elements as &$element) {
if ($element["parent_id"] != null && $elements[$element["parent_id"]] == null)
unset($element["parent_id"]);
if ($element['parent_id'] == $parentId) {
$children = buildTree($elements, $element['id']);
if ($children) {
$element['children'] = $children;
}
$branch[$element['id']] = $element;
unset($element);
}
}
return $branch;
}
回答9:
Here is my solution, works ideally, if we assume that the top level parent_id=0:
function MakeTree($arr){
$parents_arr=array();
foreach ($arr as $key => $value) {
$parents_arr[$value['pid']][$value['id']]=$value;
}
$tree=$parents_arr['0'];
$this->createTree($tree, $parents_arr);
return $tree;
}
function createTree(&$tree, $parents_arr){
foreach ($tree as $key => $value) {
if(!isset($value['children'])) {
$tree[$key]['children']=array();
}
if(array_key_exists($key, $parents_arr)){
$tree[$key]['children']=$parents_arr[$key];
$this->createTree($tree[$key]['children'], $parents_arr);
}
}
}
回答10:
This is my solution, copy and optimize others solutions.
function buildTree(array &$elements, $parentId = 0) {
$branch = array();
foreach ($elements as $key => $element) {
if ($element['parent_id'] == $parentId) {
$children = $this->buildTree($elements, $key);
if ($children) {
$element['children'] = $children;
}
$branch[$key] = $element;
unset($elements[$key]);
}
}
return $branch;
}
回答11:
Clean, short and free of ballast. Array of arrays to tree:
class Mother {
private $root;
public function treeInit($array)
{
$this->root = new Child();
foreach($array as $value){
$this->root->treeClimb(array_reverse($value));
}
return $this->root;
}
}
class Child {
private $children = [];
public function treeClimb($arr)
{
if(count($arr) > 0) {
$childTmp = array_pop($arr);
if(!key_exists($childTmp,$this->children))
{
$this->children[$childTmp] = new Child();
}
$this->children[$childTmp]->treeClimb($arr);
}
}
}
$array = array(array('obst','banae','krumm','gelb'),
array('obst','beere','him'),
array('obst','beere','brom'),
array('obst','banae','gerade'),
array('veg','carot','gerade'));
$obj = new Mother();
var_dump($obj->treeInit($array));
回答12:
I came up with a similar solution as @eugen-rieck and wanted to share it. I named $branches my array of indices, though.
$tree = [];
$branches = [];
while (!empty($input)) {
$beforeCount = count($input);
foreach ($input as $id => $item) {
$pid = $item['parent_id'];
if (isset($branches[$pid])) {
$branches[$pid]['children'][$id] = $item;
$branches[$id] = &$branches[$pid]['children'][$id];
unset($input[$id]);
}
}
if ($beforeCount === count($input)) {
$firstItem = array_shift($input);
$id = $firstItem['id'];
$tree[$id] = $firstItem;
$branches[$id] = &$tree[$id];
}
}
来源：https://stackoverflow.com/questions/8840319/build-a-tree-from-a-flat-array-in-php