PHP MySQL inserts multiple pieces of data, phpmysql inserts multiple pieces_PHP tutorial

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建链接
$conn = new mysqli($servername, $username, $password, $dbname);
// 检查链接
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('John', 'Doe', 'john@example.com');";
$sql .= "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('Mary', 'Moe', 'mary@example.com');";
$sql .= "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('Julie', 'Dooley', 'julie@example.com')";

if ($conn->multi_query($sql) === TRUE) {
    echo "New records created successfully";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建链接
$conn = mysqli_connect($servername, $username, $password, $dbname);
// 检查链接
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

$sql = "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('John', 'Doe', 'john@example.com');";
$sql .= "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('Mary', 'Moe', 'mary@example.com');";
$sql .= "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('Julie', 'Dooley', 'julie@example.com')";

if (mysqli_multi_query($conn, $sql)) {
    echo "New records created successfully";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

mysqli_close($conn);
?>

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDBPDO";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    // set the PDO error mode to exception
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 开始事务
    $conn->beginTransaction();
    // SQL 语句
    $conn->exec("INSERT INTO MyGuests (firstname, lastname, email) 
    VALUES ('John', 'Doe', 'john@example.com')");
    $conn->exec("INSERT INTO MyGuests (firstname, lastname, email) 
    VALUES ('Mary', 'Moe', 'mary@example.com')");
    $conn->exec("INSERT INTO MyGuests (firstname, lastname, email) 
    VALUES ('Julie', 'Dooley', 'julie@example.com')");

    // commit the transaction
    $conn->commit();
    echo "New records created successfully";
    }
catch(PDOException $e)
    {
    // roll back the transaction if something failed
    $conn->rollback();
    echo $sql . "<br>" . $e->getMessage();
    }

$conn = null;
?>

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} else {
    $sql = "INSERT INTO MyGuests VALUES(?, ?, ?)";

    // 为 mysqli_stmt_prepare() 初始化 statement 对象
    $stmt = mysqli_stmt_init($conn);

    //预处理语句
    if (mysqli_stmt_prepare($stmt, $sql)) {
        // 绑定参数
        mysqli_stmt_bind_param($stmt, 'sss', $firstname, $lastname, $email);

        // 设置参数并执行
        $firstname = 'John';
        $lastname = 'Doe';
        $email = 'john@example.com';
        mysqli_stmt_execute($stmt);

        $firstname = 'Mary';
        $lastname = 'Moe';
        $email = 'mary@example.com';
        mysqli_stmt_execute($stmt);

        $firstname = 'Julie';
        $lastname = 'Dooley';
        $email = 'julie@example.com';
        mysqli_stmt_execute($stmt);
    }
}
?>