mysqli 参数传递

$host = 'localhost';
$user = 'root';
$password = 'your_password';
$database = 'your_database';

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

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

echo '连接成功';

$stmt = $conn->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username); // "s" 表示参数类型为字符串
$username = $_POST['username'];
$stmt->execute();
$result = $stmt->get_result();

$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 '转账成功';
} catch (Exception $e) {
    $conn->rollback();
    echo '转账失败: ' . $e->getMessage();
}