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".
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);
}