php无限极分类实现方法分析

<?php
  //分类方法
  function make_list($parent,$deep = 0){
    global $tasks;//申明全局变量
    global $strArr;//申明全局变量
    $qianzhui = str_repeat("&nbsp;",$deep)."|--";
    foreach ($parent as $key => $value) {
      $strArr[] = $qianzhui.$value;
      if(isset($tasks[$key])){
        make_list($tasks[$key],++$deep);//递归调用函数
      }
    }
  }
  //数据库连接
  $dbc = mysqli_connect("localhost","root","1234","tasks");
  //拼接sql语句
  $q = "select task_id,parent_id,task from tasks where date_completed = '0000-00-00:00:00:00' order by parent_id,date_added asc";
  //执行sql
  $r = mysqli_query($dbc,$q);
  //遍历结果集
  while (list($task_id,$parent_id,$task) = mysqli_fetch_array($r,MYSQLI_NUM)) {
    //组成数组(一级键为parent_id,二级键为task_id,值为任务内容)
    $tasks[$parent_id][$task_id] = $task;
  }
  //打印数组
  echo "<pre>";
  print_r($tasks);
  echo "</pre>";
  make_list($tasks[0]);
  echo "<pre>";
  //打印缩进数组
  print_r($strArr);
  echo "</pre>";
?>

<?php
  function findArr($where = "parent_id = 0",$deep = 0){
    $dbc = mysqli_connect("localhost","root","1234","tasks");
    global $strArr;
    $q = "select task_id,parent_id,task from tasks where ".$where." order by parent_id,date_added asc";
    $r = mysqli_query($dbc,$q);
    $qianzhui = str_repeat("&nbsp;", $deep)."|--";
    while (list($task_id,$parent_id,$task) = mysqli_fetch_array($r,MYSQLI_NUM)) {
      $strArr[] = $qianzhui.$task;
      //拼接查询条件
      $where = "parent_id = ".$task_id;
      //递归查询
      findArr($where,++$deep);
    }
  }
  findArr();
  //打印缩进数组
  echo "<pre>";
  print_r($strArr);
  echo "</pre>";
?>