rml5fa
Last Updated: February 25, 2016
·
4.926K
· samuelm

Nested PDO transactions

When using PDO you can't have nested transactions , so if you call multiple method that have transactions in the same one , you get an error like " a transaction already started" .

To handle this it's very simple ifyou use a database that handle SAVE POINTS , just extend PDO like this

/**
 * This class extends native PDO one but allow nested transactions
 * by using the SQL statements `SAVEPOINT', 'RELEASE SAVEPOINT' AND 'ROLLBACK SAVEPOINT'
 */
class ExtendedPdo extends PDO
{

  /**
   * @var array Database drivers that support SAVEPOINT * statements.
   */
  protected static $_supportedDrivers = array("pgsql", "mysql");

  /**
   * @var int the current transaction depth
   */
  protected $_transactionDepth = 0;


  /**
   * Test if database driver support savepoints
   *
   * @return bool
   */
  protected function hasSavepoint()
  {
    return in_array($this->getAttribute(PDO::ATTR_DRIVER_NAME),
      self::$_supportedDrivers);
  }


  /**
   * Start transaction
   *
   * @return bool|void
   */
  public function beginTransaction()
  {
    if($this->_transactionDepth == 0 || !$this->hasSavepoint()) {
      parent::beginTransaction();
    } else {
      $this->exec("SAVEPOINT LEVEL{$this->_transactionDepth}");
    }

    $this->_transactionDepth++;
  }

  /**
   * Commit current transaction
   *
   * @return bool|void
   */
  public function commit()
  {
    $this->_transactionDepth--;

    if($this->_transactionDepth == 0 || !$this->hasSavepoint()) {
      parent::commit();
    } else {
      $this->exec("RELEASE SAVEPOINT LEVEL{$this->_transactionDepth}");
    }
  }

  /**
   * Rollback current transaction,
   *
   * @throws PDOException if there is no transaction started
   * @return bool|void
   */
  public function rollBack()
  {

    if ($this->_transactionDepth == 0) {
      throw new PDOException('Rollback error : There is no transaction started');
    }

    $this->_transactionDepth--;

    if($this->_transactionDepth == 0 || !$this->hasSavepoint()) {
      parent::rollBack();
    } else {
      $this->exec("ROLLBACK TO SAVEPOINT LEVEL{$this->_transactionDepth}");
    }
  }

}

enjoy .