我有一堆名称-父母名对，我想将其变成尽可能少的分层树结构。因此，例如，这些可能是配对：
Child : Parent
H : G
F : G
G : D
E : D
A : E
B : C
C : E
D : NULL
需要将其转换为一个或多个分层树：
D
├── E
│ ├── A
│ │ └── B
│ └── C
└── G
├── F
└── H
我想要的最终结果是一组嵌套<ul>元素，每个元素都<li>包含孩子的名字。
配对中没有不一致的地方（子代是它自己的父代，父代是子代的孩子，等等），因此可以进行大量优化。
在PHP中，如何从包含child => parent对的数组转到一组Nested <ul>？
我感觉涉及到递归，但是我还没有足够清醒地思考它。
Answers:
这需要一个非常基本的递归函数来将子/父对解析为树结构，并需要另一个递归函数以将其打印出来。只有一个函数就足够了，但是为了清楚起见，这里有两个（在此答案的末尾可以找到一个组合函数）。
首先初始化子对/父对对的数组：
$tree = array(
'H' => 'G',
'F' => 'G',
'G' => 'D',
'E' => 'D',
'A' => 'E',
'B' => 'C',
'C' => 'E',
'D' => null
);然后将数组解析为分层树结构的函数：
function parseTree($tree, $root = null) {
$return = array();
# Traverse the tree and search for direct children of the root
foreach($tree as $child => $parent) {
# A direct child is found
if($parent == $root) {
# Remove item from tree (we don't need to traverse this again)
unset($tree[$child]);
# Append the child into result array and parse its children
$return[] = array(
'name' => $child,
'children' => parseTree($tree, $child)
);
}
}
return empty($return) ? null : $return;
}还有遍历该树以打印出无序列表的函数：
function printTree($tree) {
if(!is_null($tree) && count($tree) > 0) {
echo '<ul>';
foreach($tree as $node) {
echo '<li>'.$node['name'];
printTree($node['children']);
echo '</li>';
}
echo '</ul>';
}
}以及实际用法：
$result = parseTree($tree);
printTree($result);这是内容$result：
Array(
[0] => Array(
[name] => D
[children] => Array(
[0] => Array(
[name] => G
[children] => Array(
[0] => Array(
[name] => H
[children] => NULL
)
[1] => Array(
[name] => F
[children] => NULL
)
)
)
[1] => Array(
[name] => E
[children] => Array(
[0] => Array(
[name] => A
[children] => NULL
)
[1] => Array(
[name] => C
[children] => Array(
[0] => Array(
[name] => B
[children] => NULL
)
)
)
)
)
)
)
)如果需要更高的效率，可以将这些功能合并为一个，并减少迭代次数：
function parseAndPrintTree($root, $tree) {
$return = array();
if(!is_null($tree) && count($tree) > 0) {
echo '<ul>';
foreach($tree as $child => $parent) {
if($parent == $root) {
unset($tree[$child]);
echo '<li>'.$child;
parseAndPrintTree($child, $tree);
echo '</li>';
}
}
echo '</ul>';
}
}您只会在这样小的数据集上保存8次迭代，但在较大的数据集上可能会有所作为。
生成树的另一个功能（不涉及递归，而是使用引用）：
$array = array('H' => 'G', 'F' => 'G', ..., 'D' => null);
function to_tree($array)
{
$flat = array();
$tree = array();
foreach ($array as $child => $parent) {
if (!isset($flat[$child])) {
$flat[$child] = array();
}
if (!empty($parent)) {
$flat[$parent][$child] =& $flat[$child];
} else {
$tree[$child] =& $flat[$child];
}
}
return $tree;
}返回这样的层次结构数组：
Array(
[D] => Array(
[G] => Array(
[H] => Array()
[F] => Array()
)
...
)
)使用递归函数可以轻松地将其打印为HTML列表。
将平面结构$tree转换为层次结构的另一种更简化的方法。只需一个临时数组即可公开它：
// add children to parents
$flat = array(); # temporary array
foreach ($tree as $name => $parent)
{
$flat[$name]['name'] = $name; # self
if (NULL === $parent)
{
# no parent, is root element, assign it to $tree
$tree = &$flat[$name];
}
else
{
# has parent, add self as child
$flat[$parent]['children'][] = &$flat[$name];
}
}
unset($flat);这就是将层次结构放入多维数组的全部步骤：
Array
(
[children] => Array
(
[0] => Array
(
[children] => Array
(
[0] => Array
(
[name] => H
)
[1] => Array
(
[name] => F
)
)
[name] => G
)
[1] => Array
(
[name] => E
[children] => Array
(
[0] => Array
(
[name] => A
)
[1] => Array
(
[children] => Array
(
[0] => Array
(
[name] => B
)
)
[name] => C
)
)
)
)
[name] => D
)如果要避免递归，则输出的重要性就不那么重要了（对于大型结构而言可能是一个负担）。
我一直想解决输出数组的UL / LI“难题”。难题是，每个项目都不知道孩子是否会跟进或需要关闭多少个前面的元素。在另一个答案中，我已经通过使用RecursiveIteratorIterator和查找getDepth()我自己编写的其他元信息来解决了该问题Iterator：将嵌套的集合模型放入<ul>但隐藏的“封闭”子树中。该答案也表明，使用迭代器可以使您非常灵活。
但是，这是一个预先排序的列表，因此不适合您的示例。另外，我一直想通过某种标准的树形结构以及HTML <ul>和<li>元素来解决此问题。
我提出的基本概念如下：
TreeNode-将每个元素抽象为一个简单的TreeNode类型，可以提供其值（例如Name）以及是否具有子元素。TreeNodesIterator- RecursiveIterator能够迭代这些集合（数组）的TreeNodes。这非常简单，因为该TreeNode类型已经知道它是否有子级以及哪些子级。RecursiveListIterator- RecursiveIteratorIterator具有在任何类型上进行递归迭代时所需的所有事件的A RecursiveIterator：
beginIteration/ endIteration-开始和主列表的末尾。beginElement/ endElement-开始，并且每个元件的端部。beginChildren/ endChildren-开始和每个孩子列表的末尾。这RecursiveListIterator仅以函数调用的形式提供这些事件。子列表（在<ul><li>列表中很常见）在其父<li>元素内打开和关闭。因此，该endElement事件在相应endChildren事件之后触发。可以对其进行更改或使其可配置，以扩大此类的使用范围。然后，将事件作为函数调用分发给装饰器对象，以使情况分开。ListDecorator-一个“装饰器”类，它只是的事件的接收者RecursiveListIterator。我从主要的输出逻辑开始。使用现在的分层$tree数组，最终代码如下所示：
$root = new TreeNode($tree);
$it = new TreeNodesIterator(array($root));
$rit = new RecursiveListIterator($it);
$decor = new ListDecorator($rit);
$rit->addDecorator($decor);
foreach($rit as $item)
{
$inset = $decor->inset(1);
printf("%s%s\n", $inset, $item->getName());
}首先，让我们看一下ListDecorator简单地包装<ul>和<li>元素的，并确定列表结构的输出方式：
class ListDecorator
{
private $iterator;
public function __construct(RecursiveListIterator $iterator)
{
$this->iterator = $iterator;
}
public function inset($add = 0)
{
return str_repeat(' ', $this->iterator->getDepth()*2+$add);
}构造函数采用正在处理的列表迭代器。inset只是帮助输出缩进的辅助函数。其余只是每个事件的输出函数：
public function beginElement()
{
printf("%s<li>\n", $this->inset());
}
public function endElement()
{
printf("%s</li>\n", $this->inset());
}
public function beginChildren()
{
printf("%s<ul>\n", $this->inset(-1));
}
public function endChildren()
{
printf("%s</ul>\n", $this->inset(-1));
}
public function beginIteration()
{
printf("%s<ul>\n", $this->inset());
}
public function endIteration()
{
printf("%s</ul>\n", $this->inset());
}
}牢记这些输出功能，这是主要的输出总结/循环，我将逐步进行介绍：
$root = new TreeNode($tree);创建TreeNode用于在以下位置开始迭代的根：
$it = new TreeNodesIterator(array($root));这TreeNodesIterator是一个RecursiveIterator使在单递归迭代$root节点。它作为数组传递，因为该类需要迭代一些内容，并允许与一组子TreeNode元素（也就是元素数组）一起重用。
$rit = new RecursiveListIterator($it);这RecursiveListIterator是RecursiveIteratorIterator提供所说事件的。要使用它，只需提供一个ListDecorator需求（上面的类）并分配给addDecorator：
$decor = new ListDecorator($rit);
$rit->addDecorator($decor);然后，一切都设置为刚好foreach在其上方并输出每个节点：
foreach($rit as $item)
{
$inset = $decor->inset(1);
printf("%s%s\n", $inset, $item->getName());
}如本例所示，整个输出逻辑封装在ListDecoratorclass和single中foreach。整个递归遍历已完全封装到提供堆叠过程的SPL递归迭代器中，这意味着在内部不执行任何递归函数调用。
基于事件ListDecorator，您可以专门修改输出并为同一数据结构提供多种类型的列表。由于数组数据已封装到中，因此甚至可以更改输入TreeNode。
完整的代码示例：
<?php
namespace My;
$tree = array('H' => 'G', 'F' => 'G', 'G' => 'D', 'E' => 'D', 'A' => 'E', 'B' => 'C', 'C' => 'E', 'D' => null);
// add children to parents
$flat = array(); # temporary array
foreach ($tree as $name => $parent)
{
$flat[$name]['name'] = $name; # self
if (NULL === $parent)
{
# no parent, is root element, assign it to $tree
$tree = &$flat[$name];
}
else
{
# has parent, add self as child
$flat[$parent]['children'][] = &$flat[$name];
}
}
unset($flat);
class TreeNode
{
protected $data;
public function __construct(array $element)
{
if (!isset($element['name']))
throw new InvalidArgumentException('Element has no name.');
if (isset($element['children']) && !is_array($element['children']))
throw new InvalidArgumentException('Element has invalid children.');
$this->data = $element;
}
public function getName()
{
return $this->data['name'];
}
public function hasChildren()
{
return isset($this->data['children']) && count($this->data['children']);
}
/**
* @return array of child TreeNode elements
*/
public function getChildren()
{
$children = $this->hasChildren() ? $this->data['children'] : array();
$class = get_called_class();
foreach($children as &$element)
{
$element = new $class($element);
}
unset($element);
return $children;
}
}
class TreeNodesIterator implements \RecursiveIterator
{
private $nodes;
public function __construct(array $nodes)
{
$this->nodes = new \ArrayIterator($nodes);
}
public function getInnerIterator()
{
return $this->nodes;
}
public function getChildren()
{
return new TreeNodesIterator($this->nodes->current()->getChildren());
}
public function hasChildren()
{
return $this->nodes->current()->hasChildren();
}
public function rewind()
{
$this->nodes->rewind();
}
public function valid()
{
return $this->nodes->valid();
}
public function current()
{
return $this->nodes->current();
}
public function key()
{
return $this->nodes->key();
}
public function next()
{
return $this->nodes->next();
}
}
class RecursiveListIterator extends \RecursiveIteratorIterator
{
private $elements;
/**
* @var ListDecorator
*/
private $decorator;
public function addDecorator(ListDecorator $decorator)
{
$this->decorator = $decorator;
}
public function __construct($iterator, $mode = \RecursiveIteratorIterator::SELF_FIRST, $flags = 0)
{
parent::__construct($iterator, $mode, $flags);
}
private function event($name)
{
// event debug code: printf("--- %'.-20s --- (Depth: %d, Element: %d)\n", $name, $this->getDepth(), @$this->elements[$this->getDepth()]);
$callback = array($this->decorator, $name);
is_callable($callback) && call_user_func($callback);
}
public function beginElement()
{
$this->event('beginElement');
}
public function beginChildren()
{
$this->event('beginChildren');
}
public function endChildren()
{
$this->testEndElement();
$this->event('endChildren');
}
private function testEndElement($depthOffset = 0)
{
$depth = $this->getDepth() + $depthOffset;
isset($this->elements[$depth]) || $this->elements[$depth] = 0;
$this->elements[$depth] && $this->event('endElement');
}
public function nextElement()
{
$this->testEndElement();
$this->event('{nextElement}');
$this->event('beginElement');
$this->elements[$this->getDepth()] = 1;
}
public function beginIteration()
{
$this->event('beginIteration');
}
public function endIteration()
{
$this->testEndElement();
$this->event('endIteration');
}
}
class ListDecorator
{
private $iterator;
public function __construct(RecursiveListIterator $iterator)
{
$this->iterator = $iterator;
}
public function inset($add = 0)
{
return str_repeat(' ', $this->iterator->getDepth()*2+$add);
}
public function beginElement()
{
printf("%s<li>\n", $this->inset(1));
}
public function endElement()
{
printf("%s</li>\n", $this->inset(1));
}
public function beginChildren()
{
printf("%s<ul>\n", $this->inset());
}
public function endChildren()
{
printf("%s</ul>\n", $this->inset());
}
public function beginIteration()
{
printf("%s<ul>\n", $this->inset());
}
public function endIteration()
{
printf("%s</ul>\n", $this->inset());
}
}
$root = new TreeNode($tree);
$it = new TreeNodesIterator(array($root));
$rit = new RecursiveListIterator($it);
$decor = new ListDecorator($rit);
$rit->addDecorator($decor);
foreach($rit as $item)
{
$inset = $decor->inset(2);
printf("%s%s\n", $inset, $item->getName());
}输出：
<ul>
<li>
D
<ul>
<li>
G
<ul>
<li>
H
</li>
<li>
F
</li>
</ul>
</li>
<li>
E
<ul>
</li>
<li>
A
</li>
<li>
C
<ul>
<li>
B
</li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
</ul>一个可能的变体是一个迭代器，它迭代任何迭代器RecursiveIterator并提供对所有可能发生的事件的迭代。然后，foreach循环内的一个switch / case可以处理事件。
有关：
好吧，首先，我将键值对的直接数组转换为分层数组
function convertToHeiarchical(array $input) {
$parents = array();
$root = array();
$children = array();
foreach ($input as $item) {
$parents[$item['id']] = &$item;
if ($item['parent_id']) {
if (!isset($children[$item['parent_id']])) {
$children[$item['parent_id']] = array();
}
$children[$item['parent_id']][] = &$item;
} else {
$root = $item['id'];
}
}
foreach ($parents as $id => &$item) {
if (isset($children[$id])) {
$item['children'] = $children[$id];
} else {
$item['children'] = array();
}
}
return $parents[$root];
}这样可以将具有parent_id和id的平面数组转换为分层数组：
$item = array(
'id' => 'A',
'blah' => 'blah',
'children' => array(
array(
'id' => 'B',
'blah' => 'blah',
'children' => array(
array(
'id' => 'C',
'blah' => 'blah',
'children' => array(),
),
),
'id' => 'D',
'blah' => 'blah',
'children' => array(
array(
'id' => 'E',
'blah' => 'blah',
'children' => array(),
),
),
),
),
);然后，只需创建一个渲染函数：
function renderItem($item) {
$out = "Your OUtput For Each Item Here";
$out .= "<ul>";
foreach ($item['children'] as $child) {
$out .= "<li>".renderItem($child)."</li>";
}
$out .= "</ul>";
return $out;
}虽然乍看之下Alexander-Konstantinov的解决方案似乎不那么容易理解，但它既是天才，又在性能上成倍地提高，但应该将其视为最佳答案。
谢谢队友，我以您的荣誉为基准，比较了本文中介绍的两种解决方案。
我有一棵必须转换的具有6个级别的@ 250k扁平树，我正在寻找一种更好的方法来避免递归迭代。
递归与参考：
// Generate a 6 level flat tree
$root = null;
$lvl1 = 13;
$lvl2 = 11;
$lvl3 = 7;
$lvl4 = 5;
$lvl5 = 3;
$lvl6 = 1;
$flatTree = [];
for ($i = 1; $i <= 450000; $i++) {
if ($i % 3 == 0) { $lvl5 = $i; $flatTree[$lvl6] = $lvl5; continue; }
if ($i % 5 == 0) { $lvl4 = $i; $flatTree[$lvl5] = $lvl4; continue; }
if ($i % 7 == 0) { $lvl3 = $i; $flatTree[$lvl3] = $lvl2; continue; }
if ($i % 11 == 0) { $lvl2 = $i; $flatTree[$lvl2] = $lvl1; continue; }
if ($i % 13 == 0) { $lvl1 = $i; $flatTree[$lvl1] = $root; continue; }
$lvl6 = $i;
}
echo 'Array count: ', count($flatTree), PHP_EOL;
// Reference function
function treeByReference($flatTree)
{
$flat = [];
$tree = [];
foreach ($flatTree as $child => $parent) {
if (!isset($flat[$child])) {
$flat[$child] = [];
}
if (!empty($parent)) {
$flat[$parent][$child] =& $flat[$child];
} else {
$tree[$child] =& $flat[$child];
}
}
return $tree;
}
// Recursion function
function treeByRecursion($flatTree, $root = null)
{
$return = [];
foreach($flatTree as $child => $parent) {
if ($parent == $root) {
unset($flatTree[$child]);
$return[$child] = treeByRecursion($flatTree, $child);
}
}
return $return ?: [];
}
// Benchmark reference
$t1 = microtime(true);
$tree = treeByReference($flatTree);
echo 'Reference: ', (microtime(true) - $t1), PHP_EOL;
// Benchmark recursion
$t2 = microtime(true);
$tree = treeByRecursion($flatTree);
echo 'Recursion: ', (microtime(true) - $t2), PHP_EOL;输出说明一切：
Array count: 255493
Reference: 0.3259289264679 (less than 0.4s)
Recursion: 6604.9865279198 (almost 2h)好吧，要解析为UL和LI，就像这样：
$array = array (
'H' => 'G'
'F' => 'G'
'G' => 'D'
'E' => 'D'
'A' => 'E'
'B' => 'C'
'C' => 'E'
'D' => 'NULL'
);
recurse_uls ($array, 'NULL');
function recurse_uls ($array, $parent)
{
echo '<ul>';
foreach ($array as $c => $p) {
if ($p != $parent) continue;
echo '<li>'.$c.'</li>';
recurse_uls ($array, $c);
}
echo '</ul>';
}但是我很乐意看到一个不需要您如此频繁地遍历数组的解决方案...
这是我想出的：
$arr = array(
'H' => 'G',
'F' => 'G',
'G' => 'D',
'E' => 'D',
'A' => 'E',
'B' => 'C',
'C' => 'E',
'D' => null );
$nested = parentChild($arr);
print_r($nested);
function parentChild(&$arr, $parent = false) {
if( !$parent) { //initial call
$rootKey = array_search( null, $arr);
return array($rootKey => parentChild($arr, $rootKey));
}else { // recursing through
$keys = array_keys($arr, $parent);
$piece = array();
if($keys) { // found children, so handle them
if( !is_array($keys) ) { // only one child
$piece = parentChild($arr, $keys);
}else{ // multiple children
foreach( $keys as $key ){
$piece[$key] = parentChild($arr, $key);
}
}
}else {
return $parent; //return the main tag (no kids)
}
return $piece; // return the array built via recursion
}
}输出：
Array
(
[D] => Array
(
[G] => Array
(
[H] => H
[F] => F
)
[E] => Array
(
[A] => A
[C] => Array
(
[B] => B
)
)
)
)父子关系嵌套数组
从数据库中获取所有记录并创建嵌套数组。
$data = SampleTable::find()->all();
$tree = buildTree($data);
print_r($tree);
public function buildTree(array $elements, $parentId = 0) {
$branch = array();
foreach ($elements as $element) {
if ($element['iParentId'] == $parentId) {
$children =buildTree($elements, $element['iCategoriesId']);
if ($children) {
$element['children'] = $children;
}
$branch[] = $element;
}
}
return $branch;
}以json格式打印类别和子类别数据
public static function buildTree(array $elements, $parentId = 0){
$branch = array();
foreach($elements as $element){
if($element['iParentId']==$parentId){
$children =buildTree($elements, $element['iCategoriesId']);
if ($children) {
$element['children'] = $children;
}
$branch[] = array(
'iCategoriesId' => $element->iCategoriesId,
'iParentId'=>$element->iParentId,
'vCategoriesName'=>$element->vCategoriesName,
'children'=>$element->children,
);
}
}
return[
$branch
];
}$tree = array(
'H' => 'G',
'F' => 'G',
'G' => 'D',
'E' => 'D',
'A' => 'E',
'B' => 'C',
'C' => 'E',
'D' => null,
'Z' => null,
'MM' =>'Z',
'KK' =>'Z',
'MMM' =>'MM',
// 'MM'=>'DDD'
);$ aa = $ this-> parseTree（$ tree）;
public function get_tress($tree,$key)
{
$x=array();
foreach ($tree as $keys => $value) {
if($value==$key){
$x[]=($keys);
}
}
echo "<li>";
foreach ($x as $ke => $val) {
echo "<ul>";
echo($val);
$this->get_tress($tree,$val);
echo "</ul>";
}
echo "</li>";
}
function parseTree($tree, $root = null) {
foreach ($tree as $key => $value) {
if($value==$root){
echo "<ul>";
echo($key);
$this->get_tress($tree,$key);
echo "</ul>";
}
}老问题了，但是我也不得不这样做，而递归的例子让我头疼。在我的数据库中，我们有一个locations表，它是一个loca_idPK（子代）和自引用loca_parent_id（父代）。
目的是用HTML表示此结构。简单的查询可以以固定的顺序返回数据，但是我发现以自然的方式显示这些数据还不够好。我真正想要的是Oracle树步行处理程序，LEVEL以帮助显示。
我决定使用“路径”的概念来唯一标识每个条目。例如：
按路径对数组进行排序应该可以更轻松地处理有意义的显示。
我意识到关联数组和排序的使用很欺骗，因为它隐藏了操作的递归复杂性，但是对我来说，这看起来更简单：
<table>
<?php
$sql = "
SELECT l.*,
pl.loca_name parent_loca_name,
'' loca_path
FROM locations l
LEFT JOIN locations pl ON l.loca_parent_id = pl.loca_id
ORDER BY l.loca_parent_id, l.loca_id
";
function print_row ( $rowdata )
{
?>
<tr>
<td>
<?=$rowdata['loca_id']?>
</td>
<td>
<?=$rowdata['loca_path']?>
</td>
<td>
<?=$rowdata['loca_type']?>
</td>
<td>
<?=$rowdata['loca_status']?>
</td>
</tr>
<?php
}
$stmt = $dbh->prepare($sql);
$stmt->execute();
$result = $stmt->get_result();
$data = $result->fetch_all(MYSQLI_ASSOC);
$printed = array();
// To get tree hierarchy usually means recursion of data.
// Here we will try to use an associate array and set a
// 'path' value to represent the hierarchy tree in one
// pass. Sorting this array by the path value should give
// a nice tree order and reference.
// The array key will be the unique id (loca_id) for each row.
// The value for each key will the complete row from the database.
// The row contains a element 'loca_path' - we will write the path
// for each row here. A child's path will be parent_path/child_name.
// For any child we encounter with a parent we look up the parents path
// using the loca_parent_id as the key.
// Caveat, although tested quickly, just make sure that all parents are
// returned first by the query.
foreach ($data as $row)
{
if ( $row['loca_parent_id'] == '' ) // Root Parent
{
$row['loca_path'] = $row['loca_name'] . '/';
$printed[$row['loca_id']] = $row;
}
else // Child/Sub-Parent
{
$row['loca_path'] = $printed[$row['loca_parent_id']]['loca_path'] . $row['loca_name'] . '/';
$printed[$row['loca_id']] = $row;
}
}
// Array with paths built, now sort then print
array_multisort(array_column($printed, 'loca_path'), SORT_ASC, $printed);
foreach ( $printed as $prow )
{
print_row ( $prow );
}
?>
</table>如何创建动态树视图和菜单
步骤1：首先，我们将在mysql数据库中创建treeview表。该表包含四个column.id是任务ID，名称是任务名称。
-
-- Table structure for table `treeview_items`
--
CREATE TABLE IF NOT EXISTS `treeview_items` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(200) NOT NULL,
`title` varchar(200) NOT NULL,
`parent_id` varchar(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=7 ;
--
-- Dumping data for table `treeview_items`
--
INSERT INTO `treeview_items` (`id`, `name`, `title`, `parent_id`) VALUES
(1, 'task1', 'task1title', '2'),
(2, 'task2', 'task2title', '0'),
(3, 'task3', 'task1title3', '0'),
(4, 'task4', 'task2title4', '3'),
(5, 'task4', 'task1title4', '3'),
(6, 'task5', 'task2title5', '5');步骤2：树视图递归方法我在树的createTreeView（）方法下面创建了一个方法，如果当前任务ID大于上一个任务ID，则调用递归。
function createTreeView($array, $currentParent, $currLevel = 0, $prevLevel = -1) {
foreach ($array as $categoryId => $category) {
if ($currentParent == $category['parent_id']) {
if ($currLevel > $prevLevel) echo " <ol class='tree'> ";
if ($currLevel == $prevLevel) echo " </li> ";
echo '<li> <label for="subfolder2">'.$category['name'].'</label> <input type="checkbox" name="subfolder2"/>';
if ($currLevel > $prevLevel) { $prevLevel = $currLevel; }
$currLevel++;
createTreeView ($array, $categoryId, $currLevel, $prevLevel);
$currLevel--;
}
}
if ($currLevel == $prevLevel) echo " </li> </ol> ";
}步骤3：创建索引文件以显示树视图。这是treeview示例的主文件，在这里我们将使用必需的参数调用createTreeView（）方法。
<body>
<link rel="stylesheet" type="text/css" href="_styles.css" media="screen">
<?php
mysql_connect('localhost', 'root');
mysql_select_db('test');
$qry="SELECT * FROM treeview_items";
$result=mysql_query($qry);
$arrayCategories = array();
while($row = mysql_fetch_assoc($result)){
$arrayCategories[$row['id']] = array("parent_id" => $row['parent_id'], "name" =>
$row['name']);
}
?>
<div id="content" class="general-style1">
<?php
if(mysql_num_rows($result)!=0)
{
?>
<?php
createTreeView($arrayCategories, 0); ?>
<?php
}
?>
</div>
</body>步骤4：创建CSS文件style.css在这里，我们将编写所有与CSS相关的类，目前我正在使用订单列表创建树形视图。您也可以在此处更改图像路径。
img { border: none; }
input, select, textarea, th, td { font-size: 1em; }
/* CSS Tree menu styles */
ol.tree
{
padding: 0 0 0 30px;
width: 300px;
}
li
{
position: relative;
margin-left: -15px;
list-style: none;
}
li.file
{
margin-left: -1px !important;
}
li.file a
{
background: url(document.png) 0 0 no-repeat;
color: #fff;
padding-left: 21px;
text-decoration: none;
display: block;
}
li.file a[href *= '.pdf'] { background: url(document.png) 0 0 no-repeat; }
li.file a[href *= '.html'] { background: url(document.png) 0 0 no-repeat; }
li.file a[href $= '.css'] { background: url(document.png) 0 0 no-repeat; }
li.file a[href $= '.js'] { background: url(document.png) 0 0 no-repeat; }
li input
{
position: absolute;
left: 0;
margin-left: 0;
opacity: 0;
z-index: 2;
cursor: pointer;
height: 1em;
width: 1em;
top: 0;
}
li input + ol
{
background: url(toggle-small-expand.png) 40px 0 no-repeat;
margin: -0.938em 0 0 -44px; /* 15px */
height: 1em;
}
li input + ol > li { display: none; margin-left: -14px !important; padding-left: 1px; }
li label
{
background: url(folder-horizontal.png) 15px 1px no-repeat;
cursor: pointer;
display: block;
padding-left: 37px;
}
li input:checked + ol
{
background: url(toggle-small.png) 40px 5px no-repeat;
margin: -1.25em 0 0 -44px; /* 20px */
padding: 1.563em 0 0 80px;
height: auto;
}
li input:checked + ol > li { display: block; margin: 0 0 0.125em; /* 2px */}
li input:checked + ol > li:last-child { margin: 0 0 0.063em; /* 1px */ }