PHP PDO Transactions? - php

Question

I have a signup page and basically I need data inserted into 4 tables. I'm new to PDO and am confused over something.
Basically if any of the inserts fail I don't want anything added to the database, that seems simple enough.
My confusion is, I need to first insert the users username, email, password etc in my users table so I can get (not sure how) using PDO the uid MySQL has given my user (auto incremented by mysql). I need the user uid MySQL gave my user for the other tables as the other tables needs the uid so everything is linked properly together. My tables are InnoDB and I have foreign keys going from users_profiles(user_uid), users_status(user_uid), users_roles(user_uid) to the users.user_uid so they are all linked together.
But at the same time I want to ensure that if for example after data is inserted in the users table (so I can get the uid MySQL gave user) that if any of the other inserts fail that it removes the data that was inserted into the users table.
I thinks it's best I show my code; I have commented out the code and have explained in the code which may make it easier to understand.
// Begin our transaction, we need to insert data into 4 tables:
// users, users_status, users_roles, users_profiles
// connect to database
$dbh = sql_con();
// begin transaction
$dbh->beginTransaction();
try {
// this query inserts data into the `users` table
$stmt = $dbh->prepare('
INSERT INTO `users`
(users_status, user_login, user_pass, user_email, user_registered)
VALUES
(?, ?, ?, ?, NOW())');
$stmt->bindParam(1, $userstatus, PDO::PARAM_STR);
$stmt->bindParam(2, $username, PDO::PARAM_STR);
$stmt->bindParam(3, $HashedPassword, PDO::PARAM_STR);
$stmt->bindParam(4, $email, PDO::PARAM_STR);
$stmt->execute();
// get user_uid from insert for use in other tables below
$lastInsertID = $dbh->lastInsertId();
// this query inserts data into the `users_status` table
$stmt = $dbh->prepare('
INSERT INTO `users_status`
(user_uid, user_activation_key)
VALUES
(?, ?)');
$stmt->bindParam(1, $lastInsertID, PDO::PARAM_STR);
$stmt->bindParam(2, $activationkey, PDO::PARAM_STR);
$stmt->execute();
// this query inserts data into the `users_roles` table
$stmt = $dbh->prepare('
INSERT INTO `users_roles`
(user_uid, user_role)
VALUES
(?, ?)');
$stmt->bindParam(1, $lastInsertID, PDO::PARAM_STR);
$stmt->bindParam(2, SUBSCRIBER_ROLE, PDO::PARAM_STR);
$stmt->execute();
// this query inserts data into the `users_profiles` table
$stmt = $dbh->prepare('
INSERT INTO `users_profiles`
(user_uid)
VALUES
(?)');
$stmt->bindParam(1, $lastInsertID, PDO::PARAM_STR);
$stmt->execute();
// commit transaction
$dbh->commit();
} // any errors from the above database queries will be catched
catch (PDOException $e) {
// roll back transaction
$dbh->rollback();
// log any errors to file
ExceptionErrorHandler($e);
require_once($footer_inc);
exit;
}
I'm new to PDO and there maybe errors or problems above I have yet to notice because I can't test yet until I figure out my problem.
I need to know how I can insert the users data in the users table first so i can get the uid MySQL gave my user
Then get the uid as I need it for the other tables
But at the same time if a query fails for whatever reason after inserting into users table that the data is also deleted from the users table aswell.

Answer 1

This function returns primary key of just inserted record: PDO::lastInsertId
You will need it for NEED_USERS_UID_FOR_HERE parameter. Use it just after INSERT statement.
Since you started a transaction, data will not be inserted into any table if any error occures provided you use InnoDB engine for your MySQL tables (MyISAM doesn't support transactions).