RollBack () and beginTransaction() not work in my PHP PDO - php

Question

RollBack () and beginTransaction() not work in my PHP PDO and my table type is innoDB. In the following code my $sql1 is correct and my $sql2 is wrong (I added d to $last_id to just make it wrong). But it still executes sql1 meaning roll back no effect. Thank you for your advice.
<?php
include 'connect.php';
// Get multiple input field's value
try {
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
// Starts our transaction
$conn->beginTransaction();
foreach ($_POST['phone'] as $value) {
$sql1 = "INSERT INTO tbl_contact_info (type)
VALUES ('$value')";
// use exec() because no results are returned
$conn->exec($sql1);
$last_id = $conn->lastInsertId();
$sql2="INSERT INTO tbl_img (img_type)
VALUES ('$dlast_id')";
$conn->exec($sql2);
}
// Commits out queries
$conn->commit();
echo "New record created successfully";
}
catch(PDOException $e)
{
// Something borked, undo the queries!!
$conn->rollBack();
echo $sql . "<br>" . $e->getMessage();
}
$conn = null;
?>

Answer 1

First of all (and sorry it it's obvious but I realised it's not always clear to everyone) SQL and PHP are different languages. MySQL Server will not react to Undefined variable notices triggered in PHP code.
Secondly, notices are not exceptions so they cannot be caught with try/catch statements. (You can certainly write a custom error handler that will throw exceptions on errors but it doesn't seem to be the case here.)