PDO::beginTransaction

    (PHP 5 >= 5.1.0, PHP 7, PHP 8, PECL pdo >= 0.1.0)

    PDO::beginTransaction — Initiates a transaction

    Description

    public PDO::beginTransaction(): bool

    Turns off autocommit mode. While autocommit mode is turned off, changes made to the database via the PDO object instance are not committed until you end the transaction by calling PDO::commit(). Calling PDO::rollBack() will roll back all changes to the database and return the connection to autocommit mode.

    Some databases, including MySQL, automatically issue an implicit COMMIT when a database definition language (DDL) statement such as DROP TABLE or CREATE TABLE is issued within a transaction. The implicit COMMIT will prevent you from rolling back any other changes within the transaction boundary.

    Parameters

    This function has no parameters.

    Return Values

    Returns true on success or false on failure.

    Errors/Exceptions

    Throws a PDOException if there is already a transaction started or the driver does not support transactions.

    Note: An exception is raised even when the PDO::ATTR_ERRMODE attribute is not PDO::ERRMODE_EXCEPTION.

    Examples

    Example #1 Roll back a transaction

    The following example begins a transaction and issues two statements that modify the database before rolling back the changes. On MySQL, however, the DROP TABLE statement automatically commits the transaction so that none of the changes in the transaction are rolled back.

    <?php
    /* Begin a transaction, turning off autocommit */
    $dbh->beginTransaction();

    /* Change the database schema and data */
    $sth = $dbh->exec("DROP TABLE fruit");
    $sth = $dbh->exec("UPDATE dessert
    SET name = 'hamburger'"    );

    /* Recognize mistake and roll back changes */
    $dbh->rollBack();

    /* Database connection is now back in autocommit mode */
    ?>

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    User Contributed Notes 16 notes

    up
    56
    steve at fancyguy dot com
    9 years ago
    The nested transaction example here is great, but it's missing a key piece of the puzzle. Commits will commit everything, I only wanted commits to actually commit when the outermost commit has been completed. This can be done in InnoDB with savepoints.

    <?php

    class Database extends PDO
    {

    protected     $transactionCount = 0;

    public function     beginTransaction()
    {
    if (!    $this->transactionCounter++) {
    return     parent::beginTransaction();
    }
    $this->exec('SAVEPOINT trans'.$this->transactionCounter);
    return     $this->transactionCounter >= 0;
    }

    public function     commit()
    {
    if (!--    $this->transactionCounter) {
    return     parent::commit();
    }
    return     $this->transactionCounter >= 0;
    }

    public function     rollback()
    {
    if (--    $this->transactionCounter) {
    $this->exec('ROLLBACK TO trans'.$this->transactionCounter + 1);
    return     true;
    }
    return     parent::rollback();
    }

    }
    up
    17
    drm at melp dot nl
    16 years ago
    In response to "Anonymous / 20-Dec-2007 03:04"

    You could also extend the PDO class and hold a private flag to check if a transaction is already started.

    class MyPDO extends PDO {
    protected $hasActiveTransaction = false;

    function beginTransaction () {
    if ( $this->hasActiveTransaction ) {
    return false;
    } else {
    $this->hasActiveTransaction = parent::beginTransaction ();
    return $this->hasActiveTransaction;
    }
    }

    function commit () {
    parent::commit ();
    $this->hasActiveTransaction = false;
    }

    function rollback () {
    parent::rollback ();
    $this->hasActiveTransaction = false;
    }

    }
    up
    29
    bitluni
    11 years ago
    You can generate problems with nested beginTransaction and commit calls.
    example:

    beginTransaction()
    do imprortant stuff
    call method
    beginTransaction()
    basic stuff 1
    basic stuff 2
    commit()
    do most important stuff
    commit()

    Won't work and is dangerous since you could close your transaction too early with the nested commit().

    There is no need to mess you code and pass like a bool which indicate if transaction is already running. You could just overload the beginTransaction() and commit() in your PDO wrapper like this:

    <?php
    class Database extends \\PDO
    {
    protected     $transactionCounter = 0;
    function     beginTransaction()
    {
    if(!    $this->transactionCounter++)
    return     parent::beginTransaction();
    return     $this->transactionCounter >= 0;
    }

    function     commit()
    {
    if(!--    $this->transactionCounter)
    return     parent::commit();
    return     $this->transactionCounter >= 0;
    }

    function     rollback()
    {
    if(    $this->transactionCounter >= 0)
    {
    $this->transactionCounter = 0;
    return     parent::rollback();
    }
    $this->transactionCounter = 0;
    return     false;
    }
    //...
    }
    ?>
    up
    12
    rjohnson at intepro dot us
    15 years ago
    If you are using PDO::SQLITE and need to support a high level of concurrency with locking, try preparing your statements prior to calling beginTransaction() and you may also need to call closeCursor() on SELECT statements to prevent the driver from thinking that there are open transactions.

    Here's an example (Windows, PHP version 5.2.8). We test this by opening 2 browser tabs to this script and running them at the same time. If we put the beginTransaction before the prepare, the second browser tab would hit the catch block and the commit would throw another PDOException indicating that transactions were still open.

    <?php
    $conn     = new PDO('sqlite:C:\path\to\file.sqlite');
    $stmt = $conn->prepare('INSERT INTO my_table(my_id, my_value) VALUES(?, ?)');
    $waiting = true; // Set a loop condition to test for
    while($waiting) {
    try {
    $conn->beginTransaction();
    for(    $i=0; $i < 10; $i++) {
    $stmt->bindValue(1, $i, PDO::PARAM_INT);
    $stmt->bindValue(2, 'TEST', PDO::PARAM_STR);
    $stmt->execute();
    sleep(1);
    }
    $conn->commit();
    $waiting = false;
    } catch(    PDOException $e) {
    if(    stripos($e->getMessage(), 'DATABASE IS LOCKED') !== false) {
    // This should be specific to SQLite, sleep for 0.25 seconds
    // and try again. We do have to commit the open transaction first though
    $conn->commit();
    usleep(250000);
    } else {
    $conn->rollBack();
    throw     $e;
    }
    }
    }

    ?>
    up
    13
    kesler dot alwin at gmail dot com
    8 years ago
    please fix in answer #116669:

    $this->exec('ROLLBACK TO trans'.$this->transactionCounter + 1);

    with

    $this->exec('ROLLBACK TO trans'.($this->transactionCounter + 1));
    up
    4
    Sbastien
    2 years ago
    A way to use transaction and prepared statement to speed-up bulk INSERTs :

    <?php

    // ...

    $insert = $pdo->prepare('INSERT INTO table (c1, c2, c3) VALUES (?, ?, ?)');
    $bulk = 3_000; // To adjust according to your data/system
    $rows = 0;

    $pdo->beginTransaction();
    while (    $entry = fgetcsv($fp)) {
    $insert->execute($entry);
    if (++    $rows % $bulk === 0) {
    $pdo->commit();
    $pdo->beginTransaction();
    }
    }
    if (    $pdo->inTransaction()) { // Remaining rows insertion
    $pdo->commit();
    }
    up
    4
    cristian at crishk dot com
    7 years ago
    OK I'm finding a solution for "NESTED" transactions in MySQL, and as you know in the MySQL documentation says that it's not possible to have transactions within transactions. I was trying to use the Database class propossed here in https://php.net/manual/en/pdo.begintransaction.php but unfortunately that's wrong for many things related to the control flow that I have been solved with the following code (LOOK THE EXAMPLE AT THE END, CarOwner)

    <?php

    class TransactionController extends \\PDO {
    public static     $warn_rollback_was_thrown = false;
    public static     $transaction_rollbacked = false;
    public function     __construct()
    {
    parent :: __construct( ... connection info ... );
    }
    public static     $nest = 0;
    public function     reset()
    {
    TransactionController :: $transaction_rollbacked = false;
    TransactionController :: $warn_rollback_was_thrown = false;
    TransactionController :: $nest = 0;
    }
    function     beginTransaction()
    {
    $result = null;
    if (    TransactionController :: $nest == 0) {
    $this->reset();
    $result = $this->beginTransaction();
    }
    TransactionController :: $nest++;
    return     $result;
    }

    public function     commit()
    {

    $result = null;

    if (    TransactionController :: $nest == 0 &&
    !    TransactionController :: $transaction_rollbacked &&
    !    TransactionController :: $warn_rollback_was_thrown) {
    $result = parent :: commit();
    }
    TransactionController :: $nest--;
    return     $result;
    }

    public function     rollback()
    {
    $result = null;
    if (    TransactionController :: $nest >= 0) {
    if (    TransactionController :: $nest == 0) {
    $result = parent :: rollback();
    TransactionController :: $transaction_rollbacked = true;
    }
    else {
    TransactionController :: $warn_rollback_was_thrown = true;
    }
    }
    TransactionController :: $nest--;
    return     $result;
    }

    public function     transactionFailed()
    {
    return     TransactionController :: $warn_rollback_was_thrown === true;
    }
    // to force rollback you can only do it from $nest = 0
    public function forceRollback()
    {
    if (    TransactionController :: $nest === 0) {
    throws new \PDOException();
    }
    }
    }

    ?>
    up
    9
    ludwig dot green at gmail dot com
    14 years ago
    be aware that you also can not use TRUNCATE TABLE as this statement will trigger a commit just like CREATE TABLE or DROP TABLE

    it is best to only use SELECT, UPDATE and DELETE within a transaction, all other statements may cause commits thus breaking the atomicity of your transactions and their ability to rollback

    obviously you can use DELETE FROM <table> instead of TRUNCATE TABLE but be aware that there are differences between both statements, for example TRUNCATE resets the auto_increment value while DELETE does not.
    up
    2
    eddi13
    9 years ago
    after TRUNCATE TABLE `table` just as DELETE FROM `table`, so if whole table was deleted, aborts the transaction. And the rollback will not be passible.
    up
    3
    dbeecher at tekops dot com
    15 years ago
    // If you need to set an ISOLATION level or LOCK MODE it needs to be done BEFORE you make the BeginTransaction() call...
    //
    // **note** you should always check result codes on operations and do error handling. This sample code
    // assumes all the calls work so that the order of operations is accurate and easy to see
    //
    // THIS IS using the PECL PDO::INFORMIX module, running on fedora core 6, php 5.2.4
    //
    // This is the correct way to address an informix -243 error (could not position within table) when there
    // is no ISAM error indicating a table corruption. A -243 can happen (if the table/indexes, etc., are ok)
    // if a row is locked. The code below sets the LOCK MODE to wait 2 minutes (120 seconds) before
    // giving up. In this example you get READ COMMITTED rows, if you don't need read committed
    // but just need to get whatever data is there (ignoring locked rows, etc.) instead of
    // "SET LOCK MODE TO WAIT 120" you could "SET ISOLATION TO DIRTY READ".
    //
    // In informix you *must* manage how you do reads because it is very easy to trigger a
    // lock table overflow (which downs the instance) if you have lots of rows, are using joins
    // and have many updates happening.
    //

    // e.g.,

    $sql= "SELECT FIRST 50 * FROM mytable WHERE mystuff=1 ORDER BY myid"; /* define SQL query */

    try /* create an exception handler */
    {
    $dbh = new PDO("informix:host=......");

    if ($dbh) /* did we connect? */
    {
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $dbh->query("SET LOCK MODE TO WAIT 120")

    # ----------------
    # open transaction cursor
    # ----------------
    if ( $dbh->beginTransaction() ) # explicitly open cursor
    {
    try /* open exception handler */
    {
    $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));

    $stmt->execute();

    while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT))
    {
    $data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\t" . $row[3] . "\t" . $row[4] . "\t" . $row[5] . "\t" . $row[6] . "\t" . $row[7] . "\n" . $row[8] ;
    //print $data;
    print_r($row);
    };

    $stmt = null;
    }
    catch (PDOException $e)
    {
    print "Query Failed!\n\n";

    print "DBA FAIL:" . $e->getMessage();
    };

    $dbh->rollback(); # abort any changes (ie. $dbh->commit()
    $dbh = null; # close connection
    }
    else
    {
    # we should never get here, it should go to the exception handler
    print "Unable to establish connection...\n\n";
    };
    };
    }
    catch (Exception $e)
    {
    $dbh->rollback();
    echo "Failed: " . $e->getMessage();
    };
    up
    2
    geompse at gmail dot com
    14 years ago
    With Oracle, any structure statement will do an implicit commit.

    So : ALTER TABLE "my_table" DROP COLUMN "my_column";
    Can't be rolled back !

    Hope this will save time for others
    up
    1
    Steel Brain
    9 years ago
    The example is misleading, Typically data definition language clauses (DDL) will trigger the database engine to automatically commit. It means that if you drop a table, that query will be executed regardless of the transaction.
    Ref-Mysql:
    https://dev.mysqlserver.cn/doc/refman/5.0/en/implicit-commit.html
    up
    -2
    arth dot inbox at mail dot ru
    10 years ago
    Strange behavior with pdo_firebird driver:

    <?php
    $dbh     = new PDO ('','','',array( PDO :: ATTR_PERSISTENT=>true));
    $dbh->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION );
    $dbh -> exec ( "select 1;" ); //should be autocommitted
    try
    {
    //$dbh->commit/rollback here fixes the issue;
    $dbh -> beginTransaction (); // <- fails "with there is already an active transaction"
    $dbh -> exec ( "select 1;" );
    $dbh -> commit ();
    }
    catch (     Exception $e )
    {
    $dbh -> rollBack ();
    }
    ?>
    up
    -5
    Anonymous
    16 years ago
    beginTransaction will through a PDOException if you execute it while a PDO transaction is already active. Additionally the PDO engine doesn't seem to provide any way of determining if there is a transaction "in flight" so if you might be calling a function from within another function that starts a transaction you'll have to wrap the beginTransaction () call in a try .. catch block.
    up
    -13
    mtjo62 at gmail dot com
    10 years ago
    For the PDO driver for the Firebird server, you have to explicitly disable autocommit to initiate the transaction as well as explicitly enable autocommit to commit it.

    $dbh->setAttribute( PDO::ATTR_AUTOCOMMIT, 0 );
    $dbh->beginTransaction();

    /** Query block */

    $dbh->commit();
    $dbh->setAttribute( PDO::ATTR_AUTOCOMMIT, 1 );
    up
    -10
    sasi dot viragelet at gmail dot com
    7 years ago
    When transaction gets your enemy:

    try {

    $pdo->beginTransaction();

    // ... whatever db actions you have and then:

    $sql_insert = 'INSERT INTO a (a_id, a_name, a_date)
    VALUES (:a_id, :a_name CURRENT_TIMESTAMP)';

    $stmt = $pdo->prepare($sql_insert);

    $stmt->bindValue(':_id', $id);
    $stmt->bindValue(':a_name', $name);

    $stmt->execute();

    $pdo->commit();

    } catch (\PDOException $e) {

    $pdo->rollBack();

    http_response_code(500);
    header("Content-type: text/plain");
    echo $e;
    exit();

    }

    Notice the sytax error? There's a missing comma that just slips through every gate of surveillance:

    "...UES (:a_id, :a_name CURR..." :: between the to be binded value and current timestamp command. The missing comma will not generate any error no syntax error, no database error. Though this record will never or partially make it. This will just silently fail. The story gets rough if you build your other dependencies on the transactions unmovable foot-stones of trust.

    Just imagine you have some basic records in your transaction that you really wanna ensure ends up correctly in your db. And these records have a foreign constraint relation with another record. (That of course if you'd include in the transaction would throw you a big red error(–for who don't get it: transaction will first attempt to write everything into a temporary place, where it will get checked before everything gets into its permanent place, so constraints cannot be checked for something that don't exist yet.)) So you have a constraint that's based on the trust PDO will throw an error if something gets screwed, so what, you'll just place that insertion after the commit was successful. (Without any doublecheck.)

    What happens you will get some partial records in your database without a relation that just might be important. You will that way be able to build up very sophisticated strange behaviours in your application. So pay attention!
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