PHP PDO - There is no active transaction - php

Question

I am having problem with transactions in php script. I would like to make multiply queries and be able to recall them all, if at least one of them fails. Below you can find a simple example of the script I am using:
$tags_input = array(6,4,5);
$conn = new PDO('mysql:host='.DB_HOST.';dbname='.DB_NAME.';charset=utf8',
DB_USER, DB_PASSW, array(
PDO::ATTR_EMULATE_PREPARES => false,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8'"));
$conn->beginTransaction();
$sql = "INSERT INTO projects (id, pr_id, enabled) VALUES ( :val0, :val1, :val2)";
$stmt = $conn->prepare($sql);
if(count($tags_input)>0){
for($i = 0;$i<count($tags_input);$i++){
$stmt->bindValue(':val0', 57);
$stmt->bindValue(':val1', $tags_input[$i]);
$stmt->bindValue(':val2', 'Y');
$result = $stmt->execute();
}
}
$res1 = $conn->commit();
$conn->rollBack();
Now, this example generates an error:
Uncaught exception 'PDOException' with message 'There is no active
transaction'
If I erase the line $conn->rollBack();, the error disappears. Therefore I cannot understand, why pdo object can't see open transaction (begintransaction and commit do not generate any errors). I also tried putting rollBack() inside the transaction, but made no difference. I was still getting an error 'There is no active transaction'.
I am running PHP 5.6 and Mysql tables on InnoDB.

Answer 1

Wrap your transaction code inside a try-catch statement.
//try {
$tags_input = array(6,4,5);
$conn = new PDO('mysql:host='.DB_HOST.';dbname='.DB_NAME.';charset=utf8',
DB_USER, DB_PASSW, array(
PDO::ATTR_EMULATE_PREPARES => false,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8'"));
} catch (Exception $e) {
die("Unable to connect: " . $e->getMessage());
}
try {
$conn->beginTransaction();
$sql = "INSERT INTO projects (id, pr_id, enabled) VALUES ( :val0, :val1, :val2)";
$stmt = $conn->prepare($sql);
if(count($tags_input)>0){
for($i = 0;$i<count($tags_input);$i++){
$stmt->bindValue(':val0', 57);
$stmt->bindValue(':val1', $tags_input[$i]);
$stmt->bindValue(':val2', 'Y');
$result = $stmt->execute();
}
}
$res1 = $conn->commit();
} catch (Exception $e) {
$conn->rollBack();
echo "Failed: " . $e->getMessage();
}
EDIT
A really well-based and straight-forward explanation of the answer was provided by Richard as a comment.
The reason you got error is because you were trying to close a transaction when it was already closed. beginTransaction opens one, and EITHER rollBack OR commit closes it. You have to avoid doing BOTH actions, meaning commit/rollback, for a single beginTransaction statement, or you'll get an error. The above try/catch code ensures that only one closing statement is executed.

Answer 2

Peter and Richards answers are already correct, but there is one little mistake in the code from the transaction structure (and i can't add a comment).
The $connection->beginTransaction() must be outside of the try-catch block. When you're start the beginTransaction() in the try-block and your Database Operations throws an exception, the catch-block doesn't know something from an active transaction. So, you get the same error:
"There is no active transaction".
So the structure should be as well:
Get the Connection.
Start the Transaction with $connection->beginTransaction()
Open the try-catch block.
The try-block contains the $connection->commit() after DB Operations.
The catch-block contains the $connection->rollback() before a throw Exception.
So your code should look like this:
$tags_input = array(6,4,5);
$conn = new PDO('mysql:host='.DB_HOST.';dbname='.DB_NAME.';charset=utf8',
DB_USER, DB_PASSW, array(
PDO::ATTR_EMULATE_PREPARES => false,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8'"));
} catch (Exception $e) {
die("Unable to connect: " . $e->getMessage());
}
//Begin Transaction
$conn->beginTransaction();
try {
$sql = "INSERT INTO projects (id, pr_id, enabled) VALUES ( :val0, :val1, :val2)";
$stmt = $conn->prepare($sql);
if(count($tags_input)>0){
for($i = 0;$i<count($tags_input);$i++){
$stmt->bindValue(':val0', 57);
$stmt->bindValue(':val1', $tags_input[$i]);
$stmt->bindValue(':val2', 'Y');
$result = $stmt->execute();
}
}
$res1 = $conn->commit();
} catch (Exception $e) {
$conn->rollBack();
echo "Failed: " . $e->getMessage();
}