Using Transactions with PDO

Commit a group of related database writes only when all operations succeed.

The objective is to understand the behavior and operational limits, not only the method name.

What It Does

Commit a group of related database writes only when all operations succeed.

Prerequisites

Use a dedicated development environment and sample data. Where a snippet uses an injected connection, repository, request value or mailer, supply it from your own application setup.

Example 1: Basic Use

A focused working pattern for this topic. Names such as $pdo, $authContext and $repo represent dependencies provided by the application unless initialized in the snippet.

<?php
$pdo->beginTransaction();
try {
    $pdo->prepare('UPDATE accounts SET balance = balance - ? WHERE id = ?')->execute([40, 1]);
    $pdo->prepare('UPDATE accounts SET balance = balance + ? WHERE id = ?')->execute([40, 2]);
    $pdo->commit();
} catch (Throwable $e) { if ($pdo->inTransaction()) $pdo->rollBack(); throw $e; }

Example 2: A Second Scenario

A second use case that adds a different operation or data flow specific to this topic.

<?php
$pdo->beginTransaction();
try { $pdo->prepare('INSERT INTO orders (user_id) VALUES (?)')->execute([$userId]); $orderId = $pdo->lastInsertId(); $pdo->prepare('INSERT INTO order_lines (order_id,sku) VALUES (?,?)')->execute([$orderId,$sku]); $pdo->commit(); }
catch (Throwable $e) { if ($pdo->inTransaction()) $pdo->rollBack(); throw $e; }

Example 3: Practical Checks

A practical validation, failure or deployment concern specific to this topic.

<?php
$pdo->beginTransaction();
try { $stmt = $pdo->prepare('UPDATE seats SET reserved = 1 WHERE id = ? AND reserved = 0'); $stmt->execute([$seatId]); if ($stmt->rowCount() !== 1) throw new RuntimeException('Already reserved'); $pdo->commit(); }
catch (Throwable $e) { if ($pdo->inTransaction()) $pdo->rollBack(); throw $e; }

Important Behavior and Edge Cases

Use rollback in the catch block, and note that DDL on MySQL can implicitly commit.

For production use, also account for error handling, data validation, resource limits and environment-specific driver behavior.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Commit a group of related database writes only when all operations succeed.
• Use rollback in the catch block, and note that DDL on MySQL can implicitly commit.
• Use this workflow as a focused starting point rather than a substitute for application-level tests.

Choose this API or pattern when its exact semantics match your task, and verify the result against the database driver and runtime used by your application.