php mysqli扩展

<?php
$host = 'localhost';
$user = 'username';
$password = 'password';
$dbname = 'database_name';

// 创建连接
$conn = new mysqli($host, $user, $password, $dbname);

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

<?php
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username);

$username = $_POST['username'];
$stmt->execute();

$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
    echo "ID: " . $row["id"]. " - 用户名: " . $row["username"]. "<br>";
}

$stmt->close();
$conn->close();
?>

<?php
$conn->begin_transaction();

try {
    $conn->query("UPDATE users SET balance = balance - 100 WHERE id = 1");
    $conn->query("UPDATE users SET balance = balance + 100 WHERE id = 2");
    $conn->commit();
    echo "事务提交成功";
} catch (Exception $e) {
    $conn->rollback();
    echo "事务回滚: " . $e->getMessage();
}
?>