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PHP PDO Transactions?

Posted by: admin April 23, 2020 Leave a comment


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

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)
                        (?, ?, ?, ?, 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);

    // 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)
                        (?, ?)');

    $stmt->bindParam(1, $lastInsertID,     PDO::PARAM_STR);
    $stmt->bindParam(2, $activationkey,    PDO::PARAM_STR);

    // this query inserts data into the `users_roles` table
    $stmt = $dbh->prepare('
                        INSERT INTO `users_roles`
                        (user_uid, user_role)
                        (?, ?)');

    $stmt->bindParam(1, $lastInsertID,      PDO::PARAM_STR);
    $stmt->bindParam(2, SUBSCRIBER_ROLE,    PDO::PARAM_STR);

    // this query inserts data into the `users_profiles` table
    $stmt = $dbh->prepare('
                        INSERT INTO `users_profiles`

    $stmt->bindParam(1, $lastInsertID,      PDO::PARAM_STR);

    // commit transaction

} // any errors from the above database queries will be catched
catch (PDOException $e) {
    // roll back transaction
    // log any errors to file

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.

1) 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

2) Then get the uid as I need it for the other tables

3) 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.


I updated code above to reflect changes that was offered by helpful members.

How to&Answers:

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).