一、使用引用
function listToTree($list, $pk = 'id', $pid = 'pid', $child = '_child', $root = 0) {
$tree = array();
if (is_array($list)) {
$refer = array();
foreach ($list as $key => $data) {
$refer[ $data[ $pk ] ] = &$list[ $key ];
}
foreach ($list as $key => $data) {
// 判断是否存在parent
$parentId = $data[ $pid ];
if ($root == $parentId) {
$tree[ $data[ $pk ] ] = &$list[ $key ];
} else {
if (isset($refer[$parentId])) {
$parent = &$refer[ $parentId ];
$parent[ $child ][ $data[ $pk ] ] = &$list[ $key ];
}
}
}
}
return $tree;
}二、直接循环排列（这个算法没引用，简单比较好理解，但是不足是，改变了数据的原始排序）
function list_to_tree2($arr, $pk = 'id', $pid = 'pid', $child = '_child', $root = 0){
foreach($arr as $key => $data){
$arr[ $data[ $pk ] ] = $data;
if( $key != $data[ $pk ] ){
unset($arr[$key]);
}
}
$ids = array_keys($arr);
arsort($ids);
foreach($ids as $key => $id){
if( in_array($arr[ $id ][ $pid ], $ids) ){
unset($ids[$key]);
$arr[ $arr[ $id ][ $pid ] ][ $child ][ $arr[ $id ][ $pk ] ] = $arr[ $id ];
unset($arr[ $id ]);
}
}
return $arr;
}