Important note: This will only detect whether a transaction has been started using beginTransaction(). It will not be able to detect transactions started by any other means, for example by executing "START TRANSACTION".
(PHP 5 >= 5.3.3, Bundled pdo_pgsql, PHP 7, PHP 8)
PDO::inTransaction — Verifica si se encuentra en una transacción
Verifica si una transacción está actualmente activa en el driver. Este método solo funciona para los drivers de bases de datos que soportan transacciones.
Esta función no contiene ningún parámetro.
Important note: This will only detect whether a transaction has been started using beginTransaction(). It will not be able to detect transactions started by any other means, for example by executing "START TRANSACTION".
With respect to SQLite, this method does not always return the correct result. This applies to errors including SQLITE_FULL, SQLITE_IOERR, SQLITE_NOMEM, SQLITE_BUSY, and SQLITE_INTERRUPT. According to the documentation, these errors can cause an automatic rollback. The method does not take this into account (because it uses PDO's internal tracking mechanism).
However, SQLite has a way to find out whether the transaction was automatically rolled back or not. By using sqlite3_get_autocommit() C-language function.
At least for MySQL/MariaDB, inTransaction shows the real state of the transaction since 8.0
In addition to what jlh says,
even with SQLite3 which automatically starts transaction,
inTransaction() only works after beginTransaction().
<?php
try{
$pdo = new PDO('sqlite:test.sql3', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
var_dump($pdo->inTransaction());echo "<br>"; // bool(false) : before beginTransaction()
$pdo->beginTransaction();
var_dump($pdo->inTransaction());echo "<br>"; // bool(true) : after beginTransaction()
$pdo->rollBack();
var_dump($pdo->inTransaction());echo "<br>"; // bool(false) : after commit() or rollBack()
}catch (PDOException $e){
echo 'PDOException: ' . $e->getMessage();
}catch (Exception | ErrorException $e){
var_dump($e);
}