在开发程序的时候，有时候，我们需要获取所有栏目（包括一级栏目、二级栏目、三级栏目等等），并按照父子关系形成树型结构。可以采取使用递归或者通过引用方式（PHP中引用类似C或者C++中的指针，只不过换一种说法而已）。
通过引用方式实现无限极分类
思路：
1.即所有待处理的数据进行包装成下标为主键id（pk）的数组，便于有pid获取对应的父栏目。
2.对包装的数据进行循环，如果为根节点，则将其引用添加到tree中，否则，将其引用添加到其父类的子元素中。这样虽然tree中，只是添加了根节点，但是每个根节点如果有子元素，其中包含了子元素的引用。故能形成树型。
代码如下
/**
* 把返回的数据集转换成Tree
* @param array $list 要转换的数据集
* @param string $pk 自增字段（栏目id）
* @param string $pid parent标记字段
* @return array
* @author dqs <[email protected]>
*/
function make_tree($list</span>,<span class="hljs-variable">$pk='id',$pid</span>=<span class="hljs-string">'pid'</span>,<span class="hljs-variable">$child='_child',$root=0){
$tree=array();
$packData=array();
foreach ($list</span> <span class="hljs-keyword">as</span> <span class="hljs-variable">$data) {
$packData</span>[<span class="hljs-variable">$data[$pk</span>]] = <span class="hljs-variable">$data;
}
foreach ($packData</span> <span class="hljs-keyword">as</span> <span class="hljs-variable">$key =>$val){
if($val</span>[<span class="hljs-variable">$pid]==$root){//代表跟节点
$tree</span>[]=& <span class="hljs-variable">$packData[$key];
}else{
//找到其父类
$packData</span>[<span class="hljs-variable">$val[$pid</span>]][<span class="hljs-variable">$child][]=& $packData</span>[<span class="hljs-variable">$key];
}
}
return $tree;
}
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数据结构如下：
执行结果如下
Array
(
[0] => Array
(
[id] => 6
[pid] => 0
[title] => 测试1
[url] => test1
[sort] => 0
[create_time] => 1464076199
[update_time] => 1464076199
[status] => 1
[target] => 0
)
[1] => Array
(
[id] => 7
[pid] => 0
[title] => 测试2
[url] => test2
[sort] => 0
[create_time] => 1464076218
[update_time] => 1464076218
[status] => 1
[target] => 0
)
[2] => Array
(
[id] => 1
[pid] => 0
[title] => 首页
[url] => Index/index
[sort] => 1
[create_time] => 1379475111
[update_time] => 1379923177
[status] => 1
[target] => 0
)
[3] => Array
(
[id] => 2
[pid] => 0
[title] => 博客
[url] => Article/index?category=blog
[sort] => 2
[create_time] => 1379475131
[update_time] => 1379483713
[status] => 1
[target] => 0
[_child] => Array
(
[0] => Array
(
[id] => 4
[pid] => 2
[title] => 个人博客
[url] => ownblog
[sort] => 0
[create_time] => 1464075558
[update_time] => 1464075558
[status] => 1
[target] => 0
[_child] => Array
(
[0] => Array
(
[id] => 8
[pid] => 4
[title] => 新浪博客
[url] => sinaBlog
[sort] => 0
[create_time] => 1464077276
[update_time] => 1464077276
[status] => 1
[target] => 0
)
)
)
[1] => Array
(
[id] => 5
[pid] => 2
[title] => 他人博客
[url] => otherBlog
[sort] => 0
[create_time] => 1464075582
[update_time] => 1464075582
[status] => 1
[target] => 0
)
)
)
[4] => Array
(
[id] => 3
[pid] => 0
[title] => 官网
[url] => http://www.onethink.cn
[sort] => 3
[create_time] => 1379475154
[update_time] => 1387163458
[status] => 1
[target] => 0
)
)
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附加OneThink中无限极分类函数
/**
* 把返回的数据集转换成Tree
* @param array $list 要转换的数据集
* @param string $pid parent标记字段
* @param string $level level标记字段
* @return array
* @author 麦当苗儿 <[email protected]>
*/
function list_to_tree($list</span>, <span class="hljs-variable">$pk='id', $pid</span> = <span class="hljs-string">'pid'</span>, <span class="hljs-variable">$child = '_child', $root = 0) {
// 创建Tree
$tree = array();
if(is_array($list)) {
// 创建基于主键的数组引用
$refer = array();
foreach ($list</span> <span class="hljs-keyword">as</span> <span class="hljs-variable">$key => $data) {
$refer</span>[<span class="hljs-variable">$data[$pk</span>]] =& <span class="hljs-variable">$list[$key];
}
foreach ($list</span> <span class="hljs-keyword">as</span> <span class="hljs-variable">$key => $data) {
// 判断是否存在parent
$parentId</span> = <span class="hljs-variable">$data[$pid];
if ($root</span> == <span class="hljs-variable">$parentId) {
$tree</span>[] =& <span class="hljs-variable">$list[$key];
}else{
if (isset($refer</span>[<span class="hljs-variable">$parentId])) {
$parent</span> =& <span class="hljs-variable">$refer[$parentId];
$parent</span>[<span class="hljs-variable">$child][] =& $list</span>[<span class="hljs-variable">$key];
}
}
}
}
return $tree;
}
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通过递归方式实现无限极分类
思路：
1.使用循环，分别获取所有的根节点。
2.在获取每个节点的时候，将该节点从原数据中移除，并递归方式获取其所有的子节点，一直原数据为空。
代码实现如下：
function make_tree1($list</span>,<span class="hljs-variable">$pk='id',$pid</span>=<span class="hljs-string">'pid'</span>,<span class="hljs-variable">$child='_child',$root=0){
$tree=array();
foreach($list</span> <span class="hljs-keyword">as</span> <span class="hljs-variable">$key=> $val){
if($val</span>[<span class="hljs-variable">$pid]==$root){
//获取当前$pid所有子类
unset($list</span>[<span class="hljs-variable">$key]);
if(! empty($list)){
$child</span>=make_tree1(<span class="hljs-variable">$list,$pk</span>,<span class="hljs-variable">$pid,$child</span>,<span class="hljs-variable">$val[$pk]);
if(!empty($child)){
$val</span>[<span class="hljs-string">'_child'</span>]=<span class="hljs-variable">$child;
}
}
$tree</span>[]=<span class="hljs-variable">$val;
}
}
return $tree;
}
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效果截图如下：
