帮我用php写一个简单的在库管理系统

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

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

// 检查连接
if ($conn->connect_error) {
  die("连接失败: " . $conn->connect_error);
}

// 创建一个名为books的表
$sql = "CREATE TABLE books (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
title VARCHAR(30) NOT NULL,
author VARCHAR(30) NOT NULL,
quantity INT(6) NOT NULL
)";

if ($conn->query($sql) === TRUE) {
  echo "Table books created successfully";
} else {
  echo "创建数据表错误: " . $conn->error;
}

// 关闭数据库连接
$conn->close();
?>