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 — Checks if inside a transaction
Checks if a transaction is currently active within the driver. This method only works for database drivers that support transactions.
This function has no parameters.
Returns true if a transaction is currently active, and false if not.
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".
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);
}