我已经挣扎了好几个小时了。我有一个两步注册表单，并将所有输入传输到会话变量，它们都在第二步工作。但是，当我尝试向第二个表插入数据时，没有存储任何内容，我也不知道为什么。

<?php
include ("encrypt.php");
$conn =  mysqli_connect($servername, $dbuser, $dbpassword, $dbname);
$problem = '';
$firstName = $_SESSION['firstName'] ;
$lastName = $_SESSION['lastName'];
$email = $_SESSION['email'];
$username= $_SESSION['username'];
$password= $_SESSION['password'];

$pass = encrypt($password);

if(isset($_POST["mysubmit"]) && ($_POST["mysubmit"]=="Submit Form")){
$dOb = mysqli_real_escape_string  ($conn, $_POST["eventDate"]);
$difficulty = mysqli_real_escape_string  ($conn, $_POST ["difficultyCatagory"]);
$club = mysqli_real_escape_string  ($conn,$_POST["clubSelect"]);
echo $dOb, $difficulty, $club, $firstName, $lastName, $email, $username,$password, $pass;

mysqli_autocommit($conn,FALSE);

mysqli_query($conn,"INSERT INTO userBMX (username,password) VALUES ('$username', '$pass')");

mysqli_query($conn,"INSERT INTO userDetailsBMX(userID, firstName, lastName, email, dateofBirth, Status, club) 
VALUES (last_insert_id(),'$firstName','$lastName','$email','$dOb','$difficulty','$club')");

mysqli_commit($conn);

echo 'stored';
/*header ("Location: login.php");*/
}
else{
    echo "ERROR: was not able to execute $conn. " . mysqli_error($conn);
}

?>