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    PDO::beginTransaction

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

    PDO::beginTransaction — Inicia una transacción

    Descripción

    public PDO::beginTransaction(): bool

    Desctiva el modo 'autocommit'. Mientras el modo 'autocommit' esté desactivado, no se consignarán los cambios realizados en la base de datos a través de una instancia de PDO hasta que se finalice la transacción con una llamada a PDO::commit(). Una llamada a PDO::rollBack() revertirá todos los cambios de la base de datos y devolverá la conexión al modo 'autocommit'.

    Algunas bases de datos, incluida MySQL, ejecután automáticamente un COMMIT implícito cuando una sentencia de definición de lenguaje de base de datos (DDL), tal como DROP TABLE o CREATE TABLE, se ejecutan en una transacción. El COMMIT implícito prevendrá de la reversión de cualquier otro cambio dentro del límite de la transacción.

    Valores devueltos

    Devuelve true en caso de éxito o false en caso de error.

    Errores/Excepciones

    Lanza una PDOException si ya hay una transacción iniciada o el controlador no admite transacciones.

    Nota: Se emite una excepción inclusi cuando el atributo PDO::ATTR_ERRMODE no es PDO::ERRMODE_EXCEPTION.

    Ejemplos

    Ejemplo #1 Revertir una transacción

    El siguiente ejemplo inicia una transacción y ejecuta dos sentencias que modifican la base de datos antes de revertir los cambios. En MySQL, sin embargo, la sentencia DROP TABLE automáticamente consigna la transacción, con lo cual, ninguno de los cambios en la transacción son revertidos.

    <?php
    /* Iniciar una transacción, desactivando 'autocommit' */
    $gbd->beginTransaction();

    /* Cambiar el esquema y datos de la base de datos */
    $gsent = $gbd->exec("DROP TABLE fruit");
    $gsent = $gbd->exec("UPDATE dessert
    SET name = 'hamburger'"    );

    /* Reconocer un error y revertir los cambios */
    $gbd->rollBack();

    /* La conexión a la base de datos ahora vuelve al modo 'autocommit' */
    ?>

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    User Contributed Notes 12 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
    31
    bitluni
    12 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
    16
    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
    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
    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
    4
    cristian at crishk dot com
    8 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 http://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
    8
    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
    3
    Sbastien
    3 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
    dbeecher at tekops dot com
    16 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
    eddi13
    10 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
    1
    Steel Brain
    10 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:
    http://dev.mysql.com/doc/refman/5.0/en/implicit-commit.html
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