php获取mysql最大自增

<?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);
}

// 查询最大自增值
$sql = "SELECT MAX(id) as max_id FROM table_name";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 输出数据
    while($row = $result->fetch_assoc()) {
        echo "最大自增值: " . $row["max_id"];
    }
} else {
    echo "0 结果";
}

// 关闭连接
$conn->close();
?>

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

try {
    $pdo = new PDO("mysql:host=$host;dbname=$dbname", $user, $password);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 查询最大自增值
    $stmt = $pdo->query("SELECT MAX(id) as max_id FROM table_name");
    $max_id = $stmt->fetchColumn();

    echo "最大自增值: " . $max_id;
} catch(PDOException $e) {
    echo "数据库连接失败: " . $e->getMessage();
}
?>

<?php
// 开始事务
$conn->begin_transaction();

try {
    $sql = "SELECT MAX(id) as max_id FROM table_name FOR UPDATE";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        while($row = $result->fetch_assoc()) {
            echo "最大自增值: " . $row["max_id"];
        }
    }

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