mysqli_rollback()函数回退当前事务
MySQL数据库具有自动提交事务的功能，如果您将其打开，则会自动保存在数据库中所做的更改；如果将其关闭，则需要使用mysqli_commit()函数显式保存更改。
mysqli_rollback()函数将当前事务滚动到最后一个保存点（或指定的保存点）。
mysqli_rollback($con, [$flags, $name]);
| 序号 | 参数及说明 |
|---|---|
| 1 | con(必需) 这是一个表示与MySQL Server的连接的对象。 |
| 2 | flags(可选) 可以是下列常量之一：
|
| 3 | name(可选) 这是一个名称值，当给定时，将作为 ROLLBACK /* name */ 执行。 |
mysqli_rollback()函数返回一个布尔值，如果操作成功，则为true，否则为false。
此函数最初是在PHP版本5中引入的，并且在所有更高版本中均可用。
以下示例演示了mysqli_rollback()函数的用法（面向过程风格）-
<?php
//建立连接
$con = mysqli_connect("localhost", "root", "password", "mydb");
//将自动提交设置为false
mysqli_autocommit($con, False);
mysqli_query($con, "CREATE TABLE IF NOT EXISTS my_team(ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Place_Of_Birth VARCHAR(255), Country VARCHAR(255))");
//将记录插入到my_team表中
mysqli_query($con, "insert into my_team values(1, 'Shikhar', 'Dhawan', 'Delhi', 'India')");
mysqli_query($con, "insert into my_team values(2, 'Jonathan', 'Trott', 'CapeTown', 'SouthAfrica')");
mysqli_query($con, "insert into my_team values(3, 'Kumara', 'Sangakkara', 'Matale', 'Srilanka')");
mysqli_query($con, "insert into my_team values(4, 'Virat', 'Kohli', 'Delhi', 'India')");
$res = mysqli_query($con, "SELECT * FROM my_team");
print("行数（提交时）: ".mysqli_affected_rows($con)."\n");
//保存更改
mysqli_commit($con);
//截断表
mysqli_query($con, "DELETE FROM my_team where id in(3,4)");
$res = mysqli_query($con, "SELECT * FROM my_team");
print("行数（回滚之前）: ".mysqli_affected_rows($con)."\n");
//回退
mysqli_rollback($con);
//表中的内容
$res = mysqli_query($con, "SELECT * FROM my_team");
print("行数(回滚后): ".mysqli_affected_rows($con));
//关闭连接
mysqli_close($con);
?>输出结果
行数（提交时）: 4 行数（回滚之前）: 2 行数(回滚后): 4
面向对象风格的此方法的语法为$con->rollback()。以下是面向对象风格中此函数的示例；
//建立连接
$con = new mysqli("localhost", "root", "password", "mydb");
//将自动提交设置为false
$con->autocommit(FALSE);
//在players表中插入一个记录
$con->query("CREATE TABLE IF NOT EXISTS players(First_Name VARCHAR(255), Last_Name VARCHAR(255), Country VARCHAR(255))");
$con->query("insert into players values('Shikhar', 'Dhawan', 'India')");
$con->query("insert into players values('Jonathan', 'Trott', 'SouthAfrica')");
//保存结果
$con->commit();
$con->query( "insert into players values('Kumara', 'Sangakkara', 'Srilanka')");
$con->query( "insert into players values('Virat', 'Kohli', 'India')");
//回退
$con->rollback();
$res = $con->query("SELECT * FROM players");
print_r($res);
//关闭连接
$res = $con -> close();
?>输出结果
mysqli_result Object ( [current_field] => 0 [field_count] => 3 [lengths] => [num_rows] => 2 [type] => 0 )
关闭自动提交，做一些查询，提交查询，然后回滚当前事务：
<?php
$connection = mysqli_connect("localhost", "root", "password", "mydb");
if (mysqli_connect_errno($connection)){
echo "连接MySQL失败: " . mysqli_connect_error();
}
mysqli_autocommit($connection,FALSE);
mysqli_query($connection, "create table test(Name VARCHAR(255), Age INT)");
mysqli_query($connection, "INSERT INTO test VALUES ('Sharukh', 25)");
mysqli_commit($connection);
mysqli_query($connection, "INSERT INTO test VALUES ('Kalyan', 30)");
mysqli_rollback($connection);
mysqli_close($connection);
?>执行以上程序后，如果验证表test的内容，则可以看到插入的记录为-
mysql> select * from test; +---------+------+ | Name | Age | +---------+------+ | Sharukh | 25 | +---------+------+ 1 row in set (0.00 sec)