利用引用和递归实现无限极分类

表结构：

实现代码：

public function findChild(&$data, $parent_id = 0) {
        $rootList = array();
        foreach ($data as $key => $val) {
            if ($val['parent_id'] == $parent_id) {
                $rootList[]   = $val;
                unset($data[$key]);
            }
        }
        return $rootList;
    }

    public function getTree(&$data, $parent_id = 0) {
        $Model = M('tiku_point');
        $childs = $this->findChild($data, $parent_id);
		
        if (empty($childs)) {
            return null;
        }
        foreach ($childs as $key => $val) {
        	$result = $Model->where("parent_id=".$val['id'])->find();
            if ($result) {
                $treeList = $this->getTree($data, $val['id']);
                if ($treeList !== null) {
                    $childs[$key]['childs'] = $treeList;
                }
            }
        }

        return $childs;
    }
//调用方法
public function getAllPoints(){
        $Model = M('tiku_point');
        $child_data = $Model->where("course_id=3")->select(); //获取所有知识点
        $data = $this->getTree($child_data,$pid = 0);
        var_dump($data);exit;
    }