<?php
// 应用公共文件
/**
 * 数据库查询结果集无限级分类
 * @param mixed $list 结果集
 * @param string $pk 主键
 * @param string $pid 父级字段名
 * @param string $child 子结果集
 * @param int $root 起始id
 * @return @return array
 */
function list_tree($list, $pk = 'id', $pid = 'pid', $child = 'child', $root = 0)
{
    $tree = [];
    foreach ($list as $key => $val) {
        if ($val[$pid] == $root) {
            unset($list[$key]);
            if (!empty($list)) {
                $children = list_tree($list, $pk, $pid, $child, $val[$pk]);
                $val[$child] = $children;
            }
            array_push($tree, $val);
        }
    }
    return $tree;
}

function make_tree($list, $pk = 'id', $pid = 'pid', $child = 'child', $root = 0)
{
    $tree=array();
    foreach ($list as $key => $val) {
        if ($val[$pid]==$root) {
            unset($list[$key]);
            if (!empty($list)) {
                $child = make_tree($list, $pk, $pid, $child, $val[$pk]);
                if (!empty($child)) {
                    $val['child']=$child;
                } else {
                    $val['child']= array();
                }
            }
            $tree[]=$val;
        }
    }
    return $tree;
}

/**
 * 获取指定月份的第一天开始和最后一天结束的时间戳
 *
 * @param int $y 年份 $m 月份
 * @return array(本月开始时间，本月结束时间)
 */
function month_frist_and_last_day($y = "", $m = ""){
    if ($y == "") $y = date("Y");
    if ($m == "") $m = date("m");
    $m = sprintf("%02d", intval($m));
    $y = str_pad(intval($y), 4, "0", STR_PAD_RIGHT);
 
    $m>12 || $m<1 ? $m=1 : $m=$m;
    $firstday = strtotime($y . $m . "01000000");
    $firstdaystr = date("Y-m-01", $firstday);
    $lastday = strtotime(date('Y-m-d 23:59:59', strtotime("$firstdaystr +1 month -1 day")));
 
    return [ "firstday" => $firstday, "lastday" => $lastday];
}

/**
 * 生成随机字符串
 */
function generate_stochastic_string($length = 16)
{
    $permitted_chars = '0123456789abcdefghijklmnopqrstuvwxyz';
    return substr(str_shuffle($permitted_chars), 0, $length);
}