PHP / MYSQL如何在事务中获取last_insert_id

表#1 – 容器：

container_id INT (PK AI)
start_time DATETIME

表#2 – 预订

reservation_id INT (PK AI) 
reservation_time DATETIME
container_id INT (FK)

PHP代码：

mysqli_query($dbc,'SET AUTOCOMMIT=0');
mysqli_query($dbc,'START TRANSACTION');

$q1 = "INSERT INTO container (start_time) VALUES
      ('2012-07-03 11:00:00')";
$q2 = "INSERT INTO reservation (reservation_time,container_id) VALUES
      ('2012-07-03 11:00:00',LAST_INSERT_ID())";

$r1 = mysqli_query($dbc,$q1);
$r2 = mysqli_query($dbc,$q2);

if ($r1 && r2){
    mysqli_query($dbc,'COMMIT');
} else {
    mysqli_query($dbc,'ROLLBACK');
}

我做错了什么？ $r2返回false. LAST_INSERT_ID()不起作用