php mysql实现行锁定

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

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

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

// 开始事务
$conn->begin_transaction();

try {
    // 使用行锁定查询并更新数据
    $sql = "SELECT amount FROM accounts WHERE id = 1 FOR UPDATE";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        $row = $result->fetch_assoc();
        $new_amount = $row['amount'] - 100;

        $update_sql = "UPDATE accounts SET amount = $new_amount WHERE id = 1";
        if ($conn->query($update_sql) === TRUE) {
            echo "更新成功";
        } else {
            throw new Exception("更新失败: " . $conn->error);
        }
    }

    // 提交事务
    $conn->commit();
} catch (Exception $e) {
    // 回滚事务
    $conn->rollback();
    echo "事务回滚: " . $e->getMessage();
}

$conn->close();
?>