PDO, Prepared Statements & Transactions

Commit every dependent change together or roll all of them back.

Build a Complete Mental Model

PDO prepared statements separate parameters from SQL code. Wrap dependent writes or deletes in a transaction, committing on success and rolling back on failure while accounting for driver limitations and DDL implicit commits.

Apply It in Real PHP

Run and test an original PDO, Prepared Statements & Transactions example with normal, boundary, invalid, and failure inputs, recording output, warnings, exceptions, and side effects.

After This Lesson

• Explain the contract and security boundary of PDO, Prepared Statements & Transactions
• Run an original working example
• Automate an invalid or failure case

<?php
$pdo->beginTransaction();
try {
    $sql = 'UPDATE accounts SET balance = balance + :change WHERE id = :id';
    $statement = $pdo->prepare($sql);
    $statement->execute(['change' => -100, 'id' => 1]);
    $statement->execute(['change' => 100, 'id' => 2]);
    $pdo->commit();
} catch (Throwable $error) {
    if ($pdo->inTransaction()) $pdo->rollBack();
    throw $error;
}

Both updates commit, or neither does.

PDO Prepared Statements — PHP Documentation Group