PHP development classification technology drop-down menu classification (1)

In this section we will introduce a simple drop-down menu classification, similar to the following:

|-- Clothing

|-- Men's clothing

|-- Women's clothing

|-- Food

## |-- Staple food

|-- Rice

|-- Non-staple food

First, we need to create a simple database test and Connect

<?php
$link = mysqli_connect('localhost','username','password','test');
mysqli_set_charset($link,"utf8");
if (!$link) {
  die("连接失败:".mysqli_connect_error());
}
?>

and then create a table class

and set the following fields:

id: It is unique, type is int, and select the primary key.

title: Name, type is varchar, length is 30.

pid: classification, type is int.

<?php
$SQL ="CREATE TABLE IF NOT EXISTS 'class' (
'id' int(10) NOT NULL,
'title' varchar(30) NOT NULL,
'pid' int(10) NOT NULL,
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8 ";
?>

Then import some test data:

<?php
$SQL = "INSERT INTO `class` (`id`, `title`, `pid`) VALUES
(1, '服饰', 0),
(2, '食品', 0),
(3, '女装', 1),
(4, '男装', 1),
(5, '主食', 2),
(6, '副食', 2),
(7, '大米', 5);"
?>

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