编辑：
之前，我曾发布过一种解决方案，可以从您提供的输出中构建多维数组，以及一种
id从特定数组中获取特定子元素的方法。现在，我已经弄清楚了如何直接从输出中检索子元素（而不必首先通过一个
buildtree()函数：
function fetch_recursive($src_arr, $currentid, $parentfound = false, $cats = array()){ foreach($src_arr as $row) { if((!$parentfound && $row['id'] == $currentid) || $row['parent_id'] == $currentid) { $rowdata = array(); foreach($row as $k => $v) $rowdata[$k] = $v; $cats[] = $rowdata; if($row['parent_id'] == $currentid) $cats = array_merge($cats, fetch_recursive($src_arr, $row['id'], true)); } } return $cats;}要使用上面的函数，只需将输出数组传递
$data给第一个参数，然后
id您要从第二个参数中检索子元素：
例如：
$list = fetch_recursive($data, 3);
哪个应该为您提供正确的数组结构
id
3（如该答案最后一个代码框中的示例所示）。
原始答案：
到目前为止，我从来没有写过一个递归函数来从此设计中构建嵌套树。我敢肯定还有很多其他人编写了类似的函数，但是这个绝对可以为您工作：
function buildtree($src_arr, $parent_id = 0, $tree = array()){ foreach($src_arr as $idx => $row) { if($row['parent_id'] == $parent_id) { foreach($row as $k => $v) $tree[$row['id']][$k] = $v; unset($src_arr[$idx]); $tree[$row['id']]['children'] = buildtree($src_arr, $row['id']); } } ksort($tree); return $tree;}此函数将在邻接表之外递归地构建树，并保持ID的升序排列。这也使
id每个父/子的成为每个信息数组的键。
这段代码：
$r = mysql_query("SELECt * FROM test ");$data = array();while($row = mysql_fetch_assoc($r)) { $data[] = $row;}echo '<pre>';print_r(buildtree($data));echo '</pre>';将输出如下内容：
Array ( [1] => Array ( [id] => 1 [name] => Electronics [parent_id] => 0 [children] => Array ( [2] => Array ( [id] => 2 [name] => Televisions [parent_id] => 1 [children] => Array ( [4] => Array ( [id] => 4 [name] => Tube [parent_id] => 2 [children] => Array() ) [5] => Array ( [id] => 5 [name] => LCD [parent_id] => 2 [children] => Array() ) [6] => Array ( [id] => 6 [name] => Plasma [parent_id] => 2 [children] => Array() ) ) ) [3] => Array ( [id] => 3 [name] => Portable Electronics [parent_id] => 1 [children] => Array ( [7] => Array ( [id] => 7 [name] => Mp3 Players [parent_id] => 3 [children] => Array ( [10] => Array ( [id] => 10 [name] => Flash[parent_id] => 7 [children] => Array() ) ) ) [8] => Array ( [id] => 8 [name] => CD Players [parent_id] => 3 [children] => Array() ) [9] => Array ( [id] => 9 [name] => 2 Way Radios [parent_id] => 3 [children] => Array() ) ) ) ) ))
要将特定对象的所有子节点放入
id一维数组中，可以使用以下函数：
function fetch_recursive($tree, $parent_id, $parentfound = false, $list = array()){ foreach($tree as $k => $v) { if($parentfound || $k == $parent_id) { $rowdata = array(); foreach($v as $field => $value) if($field != 'children') $rowdata[$field] = $value; $list[] = $rowdata; if($v['children']) $list = array_merge($list, fetch_recursive($v['children'], $parent_id, true)); } elseif($v['children']) $list = array_merge($list, fetch_recursive($v['children'], $parent_id)); } return $list;}基于上面的
buildtree()函数，假设我们要获取所有
id3 个子节点：
echo '<pre>';print_r(fetch_recursive(buildtree($a), 3));echo '</pre>';
这将输出：
Array( [0] => Array ( [id] => 3 [name] => Portable Electronics [parent_id] => 1 ) [1] => Array ( [id] => 7 [name] => Mp3 Players [parent_id] => 3 ) [2] => Array ( [id] => 10 [name] => Flash [parent_id] => 7 ) [3] => Array ( [id] => 8 [name] => CD Players [parent_id] => 3 ) [4] => Array ( [id] => 9 [name] => 2 Way Radios [parent_id] => 3 ))
