私は別の問題を抱えていて、このページで私に合った解決策を見つけることができませんでした. ツリーを作成する必要がありましたが、ルート id を知りませんでした。これは、フラットな配列を調べて、ツリーの一番上にある最も親のアイテムでブランチを構築する必要があることを意味します。
他の誰かがルートの親アイテム ID なしでツリーを構築する必要がある場合は、次のようにしました。
<?php
$rows = [
(object) [
'id' => 1001,
'parentid' => 1000,
'name' => 'test1.1'
],
(object) [
'id' => 1000,
'parentid' => 100,
'name' => 'test1'
],
(object) [
'id' => 1002,
'parentid' => 1000,
'name' => 'test1.2'
],
(object) [
'id' => 1004,
'parentid' => 1001,
'name' => 'test1.1.1'
],
(object) [
'id' => 1005,
'parentid' => 1004,
'name' => 'test1.1.1.1'
],
(object) [
'id' => 100,
'parentid' => 10,
'name' => 'test 0'
],
(object) [
'id' => 1006,
'parentid' => 1002,
'name' => 'test1.2.1'
],
(object) [
'id' => 1007,
'parentid' => 1002,
'name' => 'test1.2.2'
],
];
function add_child(stdClass $parent, stdClass $child) {
if ($child->parentid != $parent->id) {
throw new Exception('Attempting to add child to wrong parent');
}
if (empty($parent->children)) {
$parent->children = [];
} else {
// Deal where already in branch.
foreach ($parent->children as $idx => $chd) {
if ($chd->id === $child->id) {
if (empty($chd->children)) {
// Go with $child, since $chd has no children.
$parent->children[$idx] = $child;
return;
} else {
if (empty($child->children)) {
// Already has this child with children.
// Nothing to do.
return;
} else {
// Both childs have children - merge them.
$chd->children += $child->children;
$parent->children[$idx] = $child;
return;
}
}
}
}
}
$parent->children[] = $child;
}
function build_branch(&$branch, &$rows, &$parent = null) {
$hitbottom = false;
while (!$hitbottom) {
$foundsomething = false;
// Pass 1 - find children.
$removals = []; // Indexes of rows to remove after this loop.
foreach ($rows as $idx => $row) {
if ($row->parentid === $branch->id) {
// Found a child.
$foundsomething = true;
// Recurse - find children of this child.
build_branch($row, $rows, $branch);
add_child($branch, $row);
$removals[] = $idx;
}
}
foreach ($removals as $idx) {
unset($rows[$idx]);
}
// Pass 2 - find parents.
if ($parent === null) {
$foundparent = false;
foreach ($rows as $idx => $row) {
if ($row->id === $branch->parentid) {
// Found parent
$foundsomething = true;
$foundparent = true;
add_child($row, $branch);
unset ($rows[$idx]);
// Now the branch needs to become the parent since parent contains branch.
$branch = $row;
// No need to search for other parents of this branch.
break;
}
}
}
$hitbottom = !$foundsomething;
}
}
function build_tree(array $rows) {
$tree = [];
while (!empty($rows)) {
$row = array_shift($rows);
build_branch($row, $rows);
$tree[] = $row;
}
return $tree;
}
$tree = build_tree($rows);
print_r($tree);