PHP递归实现层级树状展开

$db = mysql_connect('localhost','root','root') or die('Can't connect to database');
mysql_select_db('test') or die('Can't find database : test');
$result = mysql_query('select id,fid,name from tree');
while($arr = mysql_fetch_array($result)){
$data[] = array(
'id' => $arr['id'],'fid' => $arr['fid'],'name' => $arr['name'],);
}

// 将数据按照缩进简单排列 见图1
function data2arr($tree,$rootId = 0,$level = 0) {
foreach($tree as $leaf) {
if($leaf['fid'] == $rootId) {
echo str_repeat('',$level) . $leaf['id'] . ' ' . $leaf['name'] . '
';
foreach($tree as $l) {
if($l['fid'] == $leaf['id']) {
data2arr($tree,$leaf['id'],$level + 1);
break;
}
}
}
}
}

data2arr($data);
echo '
-----------------------------------------------------------------------
';

// 将数据按照所属关系封装 见图2
function arr2tree($tree,$rootId = 0) {
$return = array();
foreach($tree as $leaf) {
if($leaf['fid'] == $rootId) {
foreach($tree as $subleaf) {
if($subleaf['fid'] == $leaf['id']) {
$leaf['children'] = arr2tree($tree,$leaf['id']);
break;
}
}
$return[] = $leaf;
}
}
return $return;
}

$tree = arr2tree($data);
print_r($tree);
echo '
-----------------------------------------------------------------------
';

// 将数据使用HTML再次展现 见图3
function tree2html($tree) {
echo '

';
foreach($tree as $leaf) {
echo '
• ' .$leaf['name'];
  if(! emptyempty($leaf['children'])) tree2html($leaf['children']);
  echo '
';
}
echo '

';
}

tree2html($tree);