階層構造のデータベースをツリービューで表示する方法は？

Question

いくつかの理由から、mysqlデータベースのデータを2つの異なるツリービューで表示する必要があります。

例

（リストタグを使用して）ツリービュー1：

<li>level1 (Root) 
 
\t <ul> 
 
\t \t <li>level2</li> 
 
\t \t <li>level2 
 
\t \t \t <ul> 
 
\t \t \t \t <li>level3</li> 
 
\t \t \t \t <li>level3 
 
\t \t \t \t \t <ul> 
 
\t \t \t \t \t \t <li>level4</li> 
 
\t \t \t \t \t \t <li>level4</li> 
 
\t \t \t \t \t </ul> 
 
\t \t \t \t </li> 
 
\t \t \t </ul> 
 
\t \t </li> 
 
\t \t <li>level2 
 
\t \t \t <ul> 
 
\t \t \t \t <li>level3</li> 
 
\t \t \t \t <li>level3 
 
\t \t \t \t \t <ul> 
 
\t \t \t \t \t \t <li>level4</li> 
 
\t \t \t \t \t \t <li>level4</li> 
 
\t \t \t \t \t </ul> 
 
\t \t \t \t </li> 
 
\t \t \t </ul> 
 
\t \t </li> 
 
\t </ul> 
 
</li>

ツリービュー2：

私は現在、このPHPスクリプトに取り組んでいます：

<?php 
$servername = "localhost"; 
$username = "root"; 
$password = "psswd_here"; 
$dbname = "db_here"; 

$conn = new mysqli($servername, $username, $password, $dbname); 

if ($conn->connect_error) 
{ 
    die("Connection failed: " . $conn->connect_error); 
} 

$data = array(); 
$index = array(); 
$sql2 = "SELECT * FROM categories ORDER BY name"; 
$result2 = $conn->query($sql2); 

if ($result2->num_rows > 0) 
{ 
     while ($row2 = $result2->fetch_assoc()) 
     { 
       $id = $row2["id"]; 
       $parent_id = $row2["parent_id"] === NULL ? "NULL" : $row2["parent_id"]; 
       $data[$id] = $row2; 
       $index[$parent_id][] = $id; 
     } 
} 
else 
{ 
    echo "0 results"; 
} 

$conn->close(); 

function display_child_nodes($parent_id, $level) 
{ 
    global $data, $index; 
    $parent_id = $parent_id === NULL ? "NULL" : $parent_id; 
    if (isset($index[$parent_id])) 
     { 
     foreach ($index[$parent_id] as $id) 
       { 
      echo str_repeat("-", $level) . $data[$id]["name"] . "<br>"; 
      display_child_nodes($id, $level + 1); 
     } 
    } 
} 

echo '<ul>'; 
display_child_nodes(NULL, 0); 
echo '</ul>'; 
?> 

はOUTPUT：

Electronics 
-Cameras and Photography 
--Accessories 
--Camcorders 
--Digital Cameras 
-Cell Phones and Accessories 
--Accessories 
--Cell Phones 
--Smartphones 
-Computers and Tablets 
--Desktops 
--Laptops 
--Netbooks 
--Tablets 
---Android 
---iPad 
-TV and Audio 
--Home Audio 
--Speakers and Subwoofers 
--Televisions 
---CRT 
---LCD 
---LED 
---Plasma 

ここでは、データベースのスキーマがあります。..

-- phpMyAdmin SQL Dump 
-- version 4.4.12 
-- http://www.phpmyadmin.net 
-- 
-- Host: 127.0.0.1 
-- Generation Time: Oct 21, 2015 at 09:16 AM 
-- Server version: 5.6.25 
-- PHP Version: 5.6.11 

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO"; 
SET time_zone = "+00:00"; 


/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */; 
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */; 
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */; 
/*!40101 SET NAMES utf8mb4 */; 

-- 
-- Database: `binary` 
-- 

-- -------------------------------------------------------- 

-- 
-- Table structure for table `categories` 
-- 

CREATE TABLE IF NOT EXISTS `categories` (
    `id` int(10) NOT NULL, 
    `parent_id` int(10) DEFAULT NULL, 
    `name` varchar(50) COLLATE utf8_unicode_ci DEFAULT NULL 
) ENGINE=InnoDB AUTO_INCREMENT=25 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; 

-- 
-- Dumping data for table `categories` 
-- 

INSERT INTO `categories` (`id`, `parent_id`, `name`) VALUES 
(1, NULL, 'Electronics'), 
(2, 1, 'Cameras and Photography'), 
(3, 1, 'Computers and Tablets'), 
(4, 1, 'Cell Phones and Accessories'), 
(5, 1, 'TV and Audio'), 
(6, 2, 'Digital Cameras'), 
(7, 2, 'Camcorders'), 
(8, 2, 'Accessories'), 
(9, 3, 'Laptops'), 
(10, 3, 'Desktops'), 
(11, 3, 'Netbooks'), 
(12, 3, 'Tablets'), 
(13, 4, 'Cell Phones'), 
(14, 4, 'Smartphones'), 
(15, 4, 'Accessories'), 
(16, 5, 'Televisions'), 
(17, 5, 'Home Audio'), 
(18, 5, 'Speakers and Subwoofers'), 
(19, 16, 'CRT'), 
(20, 16, 'LCD'), 
(21, 16, 'LED'), 
(22, 16, 'Plasma'), 
(23, 12, 'Android'), 
(24, 12, 'iPad'); 

-- 
-- Indexes for dumped tables 
-- 

-- 
-- Indexes for table `categories` 
-- 
ALTER TABLE `categories` 
    ADD PRIMARY KEY (`id`); 

-- 
-- AUTO_INCREMENT for dumped tables 
-- 

-- 
-- AUTO_INCREMENT for table `categories` 
-- 
ALTER TABLE `categories` 
    MODIFY `id` int(10) NOT NULL AUTO_INCREMENT,AUTO_INCREMENT=25; 
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */; 
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */; 
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */; 

Answer 1

は

below-私のコードを参照してください。

あなたはあなたの正確なデザインのためにここにCSSを入れる必要があります

$servername = "localhost"; 
$username = "root"; 
$password = "psswd_here"; 
$dbname = "db_here"; 

$conn = new mysqli($servername, $username, $password, $dbname); 

if ($conn->connect_error) 
{ 
    die("Connection failed: " . $conn->connect_error); 
} 

function getCategory($parent_id){ 
    global $conn; 
    $sql2 = "SELECT * FROM categories WHERE parent_id='".$parent_id."' ORDER BY name"; 
    $result2 = $conn->query($sql2); 

    if (mysqli_num_rows($result2) > 0) 
    { 
     echo "<ul>"; 
     while ($row2 = mysqli_fetch_object($result2)) 
     { 
      echo "<li>".$row2->name."</li>"; 
      getCategory($row2->id);  
     } 
     echo "</ul>"; 
    } 
} 


//Set Parent id 
$parent_id = 0; 
getCategory($parent_id); 

注：ルートカテゴリのPARENT_IDは0