#php 递归获取下级元素#

场景：从数据库中查询出来的数据，存在上下级关系，并且层级不确定，需要把查询出来的数据组织成tree结构。以下是示例代码

/**
 * @param $data
 * @param int $pid
 * @return array
 * 递归
 * 题目-学生答题-tree
 * author by liugong
 */
public function  getRecursionHistoryChild($data, $pid = 0){

    $childrenId_data = array();
    if (empty($data)) {
        return [];
    }
    foreach ($data as $key => $val) {
        if ($val['question_pid'] == $pid) {
            $item = [] ;
            $item["question_id"] = $val['question_id'] ;
            $item["score"] = $val['score'] ;
            $item["child"] = $this ->getRecursionHistoryChild($data, $val['question_id']);
            $childrenId_data[] = $item;
            unset($data[$key]);
        }
    }
    return $childrenId_data;
}