我正在尝试从源数组生成一个多级HTML列表，格式如下：
/**
* id = unique id
* parent_id = "id" that this item is directly nested under
* text = the output string
*/
$list = array(
array(
'id' => 1,
'parent_id' => 0,
'text' => 'Level 1',
), array(
'id' => 2,
'parent_id' => 0,
'text' => 'Level 2',
), array(
'id' => 3,
'parent_id' => 2,
'text' => 'Level 2.1',
), array(
'id' => 4,
'parent_id' => 2,
'text' => 'Level 2.2',
), array(
'id' => 5,
'parent_id' => 4,
'text' => 'Level 2.2.1',
), array(
'id' => 6,
'parent_id' => 0,
'text' => 'Level 3',
)
);
目标是具有无限深度的嵌套<ul>。上面数组的预期输出是：
如果只有数组项有一个名为child的键或者包含实际子数组的键，那么通过这些可以很容易地递归并使用如下函数得到所需的输出：
function makeList($list)
{
echo '<ul>';
foreach ($list as $item)
{
echo '<li>'.$item['text'];
if (isset($item['child']))
{
makeList($item['child']);
}
echo '</li>';
}
echo '</ul>';
}
不幸的是，对我来说并非如此 - 源数组的格式无法更改。因此，很久以前我写了这个非常讨厌的函数来实现它，它只能工作三个级别（代码是逐字粘贴原始注释）。我知道这是一个漫长无聊的读物，请耐心等待：
function makeArray($links)
{
// Output
$nav = array();
foreach ($links as $k => $v)
{
// If no parent_id is present, we can assume it is a top-level link
if (empty($v['parent_id']))
{
$id = isset($v['id']) ? $v['id'] : $k;
$nav[$id] = $v;
// Remove from original array
unset($links[$k]);
}
}
// Loop through the remaining links again,
// we can assume they all have a parent_id
foreach ($links as $k => $v)
{
// Link's parent_id is in the top level array, so this is a level-2 link
// We already looped through every item so we know they are all accounted for
if (isset($nav[$v['parent_id']]))
{
$id = isset($v['id']) ? $v['id'] : $k;
// Add it to the top level links as a child
$nav[$v['parent_id']]['child'][$id] = $v;
// Set a marker so we know which ones to loop through to add the third level
$nav2[$id] = $v;
// Remove it from the array
unset($links[$k]);
}
}
// Last iteration for the third level
// All other links have been removed from the original array at this point
foreach ($links as $k => $v)
{
$id = isset($v['id']) ? $v['id'] : $k;
// Link's parent_id is in the second level array, so this is a level-3 link
// Orphans will be ignored
if (isset($nav2[$v['parent_id']]))
{
// This part is crazy, just go with it
$nav3 = $nav2[$v['parent_id']]['parent_id'];
$nav[$nav3]['child'][$v['parent_id']]['child'][] = $v;
}
}
return $nav;
}
这使得数组如下：
array(
'text' => 'Level 1'
'child' => array(
array(
'text' => 'Level 1.2'
'child' => array(
array(
'text' => 'Level 1.2.1'
'child' => array(
// etc.
),
array(
'text' => 'Level 1.2.2'
'child' => array(
// etc.
),
)
)
)
)
);
用法：
$nav = makeArray($links);
makeList($nav);
我花了很多时间试图解决这个问题，我在这里给出的原始代码仍然是我能够制作的最佳解决方案。
如果没有那个糟糕的功能（限制在3的深度），并且具有无限多个级别，我怎样才能实现这一点？对此有更优雅的解决方案吗？
答案 0 :(得分：7)
打印：
function printListRecursive(&$list,$parent=0){
$foundSome = false;
for( $i=0,$c=count($list);$i<$c;$i++ ){
if( $list[$i]['parent_id']==$parent ){
if( $foundSome==false ){
echo '<ul>';
$foundSome = true;
}
echo '<li>'.$list[$i]['text'].'</li>';
printListRecursive($list,$list[$i]['id']);
}
}
if( $foundSome ){
echo '</ul>';
}
}
printListRecursive($list);
创建多维数组：
function makeListRecursive(&$list,$parent=0){
$result = array();
for( $i=0,$c=count($list);$i<$c;$i++ ){
if( $list[$i]['parent_id']==$parent ){
$list[$i]['childs'] = makeListRecursive($list,$list[$i]['id']);
$result[] = $list[$i];
}
}
return $result;
}
$result = array();
$result = makeListRecursive($list);
echo '<pre>';
var_dump($result);
echo '</pre>';
答案 1 :(得分：4)
经过测试和工作：）
$list = array(...);
$nested = array();
foreach ($list as $item)
{
if ($item['parent_id'] == 0)
{
// Woot, easy - top level
$nested[$item['id']] = $item;
}
else
{
// Not top level, find it's place
process($item, $nested);
}
}
// Recursive function
function process($item, &$arr)
{
if (is_array($arr))
{
foreach ($arr as $key => $parent_item)
{
// Match?
if (isset($parent_item['id']) && $parent_item['id'] == $item['parent_id'])
{
$arr[$key]['children'][$item['id']] = $item;
}
else
{
// Keep looking, recursively
process($item, $arr[$key]);
}
}
}
}
答案 2 :(得分：1)
我最近写的一些方法，也许有些方法会有所帮助，对不起，我的时间很短，无法根据您的需要重新编写。
此代码实际上是Kohana框架模型的一部分，方法->as_array()用于平展Database_Result对象。
function array_tree($all_nodes){
$tree = array();
foreach($all_nodes as $node){
$tree[$node->id]['fields'] = $node->as_array();
$tree[$node->id]['children'] = array();
if($node->parent_id){
$tree[$node->parent_id]['children'][$node->id] =& $tree[$node->id];
}
}
$return_tree = array();
foreach($tree as $node){
if($node['fields']['depth'] == 0){
$return_tree[$node['fields']['id']] = $node;
}
}
return $return_tree;
}
array_tree()用于从平面阵列中制作树。关键特征是=&部分;）
function html_tree($tree_array = null){
if( ! $tree_array){
$tree_array = $this -> array_tree();
}
$html_tree = '<ul>'."\n";
foreach($tree_array as $node){
$html_tree .= $this->html_tree_crawl($node);
}
$html_tree .= '</ul>'."\n";
return $html_tree;
}
function html_tree_crawl($node){
$children = null;
if(count($node['children']) > 0){
$children = '<ul>'."\n";
foreach($node['children'] as $chnode){
$children .= $this->html_tree_crawl($chnode);
}
$children .= '</ul>'."\n";
}
return $this->html_tree_node($node, $children);
}
html_tree_node()是一种在HTML中显示当前节点和子节点的简单方法。
示例如下：
<li id="node-<?= $node['id'] ?>">
<a href="#"><?= $node['title'] ?></a>
<?= (isset($children) && $children != null) ? $children : '' ?>
</li>