How to use mysqli transactions with PHP 5.4.x and MySql

A transaction symbolizes a unit of work performed within a database management system (or similar system) against a database, and treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in database. Transactions in a database environment have two main purposes:

• To provide reliable units of work that allow correct recovery from failures and keep a database consistent even in cases of system failure, when execution stops (completely or partially) and many operations upon a database remain uncompleted, with unclear status.
• To provide isolation between programs accessing a database concurrently. If this isolation is not provided, the program’s outcome are possibly erroneous. – Wikipedia

Any time you have a unit of work that is either sensitive to outside changes or needs the ability to rollback every change, if an error occurs, you have to use a transaction.

The strategy I use when working with transactions is the following:

TRY
{
	DB->BEGIN_TRANSACTION
	RES = FIRST_QUERY
	IF(RES = ERR)
		THROW  EXCEPTION
	RES = SECOND_QUERY
	IF(RES = ERR)
		THROW  EXCEPTION
	DB->COMMIT
}
CATCH (EXCEPTION E)
{
	DB->ROLLBACK
}

Using php 5.4.x the DB->BEGIN_TRANSACTION is performed by
$mysqli_connection->autocommit(FALSE);

the DB->COMMIT is performed by

and the DB->ROLLBACK is performed by
$mysqli_connection->rollback();
$mysqli_connection->autocommit(TRUE);

The following function inserts the same value into two different table, if one of the two queries fails the databaase will be restored to initial state.

<?php
public function myTransactionFunction($param)
{
	// BEGIN TRANSACTION
	$mysqli_connection->autocommit(FALSE);
	try
	{
		// Insert new username in table1
		$stmt1 = $mysqli_connection->prepare("INSERT INTO table1(username) VALUES(?)");
		if(!$stmt1)
			throw new Exception("prepare query 1");

		$result = $stmt1->bind_param("s", $param);
		if(!$result)
			throw new Exception("bind_param query 1");

		$result = $stmt1->execute();
		if(!$result)
			throw new Exception("execute query 1");
		$stmt1->close();

		// Insert new username in table2
		$stmt2 = $mysqli_connection->>prepare("INSERT INTO table2(username) VALUES(?)");
		if(!$stmt2)
			throw new Exception("prepare query 2");

		$result = $stmt2->bind_param("s", $param);
		if(!$result)
			throw new Exception("bind_param query 2");

		$result = $stmt2->execute();
		if(!$result)
			throw new Exception("execute query 2");

		$stmt2->close();

		// COMMIT QUERIES
		$mysqli_connection->autocommit(TRUE);
		return(true);
	}
	catch( Exception $e )
	{
		$mysqli_connection->rollback();
		$mysqli_connection->autocommit(TRUE);
		echo("Error: ".$e->getMessage());
		return(false);
	}
}

?>

Gg1