Canceling Changes with the rollBack() Method

The rollBack() method cancels the currently active transaction and reverts the database back to the exact state it was in before beginTransaction() was called. This is crucial for operations where multiple commands must succeed together (e.g., a money transfer: deducting from one account and adding to another). If any of those steps fail, rollBack() ensures that the database does not end up in an inconsistent or partially updated state.

EXAMPLE

<?php
class Database {
    private $server = "localhost";
    private $username = "root";
    private $password = "";
    private $db_name = "pdo_db";
    public $connection;

    public function __construct() {
        try {
            // Added charset=utf8mb4 for character support
            $dsn = "mysql:host=" . $this->server . ";dbname=" . $this->db_name . ";charset=utf8mb4";
            $this->connection = new PDO($dsn, $this->username, $this->password);
            $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        } catch(PDOException $e) {
            die("Connection failed: " . $e->getMessage());
        }
    }

    public function safeInsertion() {
        try {
            $this->connection->beginTransaction();
            
            // First entry
            $this->connection->exec("INSERT INTO users (first_name, last_name) VALUES ('Test', 'User')");
            
            // Intentionally triggering an error (table does not exist)
            $this->connection->exec("INSERT INTO nonexistent_table (something) VALUES (1)");
            
            $this->connection->commit();
            echo "Data has been saved.";
        } catch (Exception $e) {
            // Something went wrong, rollback everything!
            $this->connection->rollBack();
            echo "Error! All changes have been rolled back: " . $e->getMessage();
        }
    }
}

// PART 3: Usage
$db = new Database();
$db->safeInsertion();
?>

RESULT

The result will be displayed here...

Practical Application: This method is almost always used inside a catch block. When PHP detects an error (an exception), it automatically triggers a rollback of all commands already sent to the database during that specific transaction. Check the process at home by following these steps:

Start the Apache and MySQL modules in the XAMPP control panel.
The method returns a boolean value (true/false) depending on the success of the rollback.
Try inserting data into a non-existent table within a transaction and observe how rollBack prevents the insertion of all other data.
Insert the example below into a PHP file and test the error simulation.