MySQLデータベースへのPHPの簡単な接続操作

<?php
        $servername = "localhost";
        $username = "root";
        // 创建连接
        $conn = mysqli_connect($servername, $username);
        // 检测连接
        if (!$conn) {

            die("连接失败: " . mysqli_connect_error());
        }

        // 创建数据库
        $sql = "CREATE DATABASE myDB";
        if (mysqli_query($conn, $sql)) {
            echo "数据库创建成功";
        } else {
            //数据库已经存在
            echo "Error creating database: " . mysqli_error($conn);
        }

        mysqli_close($conn);
        ?>

// 使用 sql 创建数据表
        $sql = "CREATE TABLE MyGuests (
        id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
        firstname VARCHAR(30) NOT NULL,
        lastname VARCHAR(30) NOT NULL,
        email VARCHAR(50),
        reg_date TIMESTAMP
        )";

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