BeginTransaction can not work in PHP mysql - php

Question

I want to insert data into CLOUD and IDC tables.
Cloudid is the foreign key of IDC table, so i want to use transaction.
Before $conn->beginTransaction(); and $conn->commit(); are added ,it works fine, but without them, it works fine.
Here is my code:
<?php
if($_GET["act"]=="add")
{
try
{
$conn=new PDO('mysql:host=localhost;port=3306;dbname=xxx' , 'root' , 'xxxx');
//$conn->beginTransaction();
$query="
insert into CLOUD (name,date) VALUES('".$_POST['customerName']."','".$_POST['firstDay']."');
insert into IDC (name,id,phone,cloudid) VALUES('".$_POST['engName3']."','".$_POST['engID3']."','".$_POST['engPhone3']."',LAST_INSERT_ID());
insert into IDC (name,id,phone,cloudid) VALUES('".$_POST['engName4']."','".$_POST['engID4']."','".$_POST['engPhone4']."',LAST_INSERT_ID());
";
$stmt=$conn->query($query);
//$conn->commit();
echo "success";
}
catch(PDOException $e)
{
$conn->rollBack();
echo "connect failed!".$e->getMesage();
exit;
}
}
?>

Answer 1

Transactions are only available when the database uses InnoDB as the storage engine. You are probably using MyISAM
Have a look here for more details on the difference between the storage engines https://dev.mysql.com/doc/refman/5.7/en/storage-engines.html
As a side note, your code is vulnerable to SQL injections because you use raw post data in non prepared queries. you should have a look there : How can I prevent SQL injection in PHP?

Answer 2

Try to initiate your connection and get last inserted id like below, also i would recommend you to use prepared statements (see http://php.net/manual/ru/pdo.prepare.php):
if($_GET["act"]=="add")
{
try {
$dbh = new PDO('mysql:host=localhost;port=3306;dbname=xxx', 'root', 'xxx',
array(PDO::ATTR_PERSISTENT => true));
echo "Connected\n";
} catch (Exception $e) {
die("Unable to connect: " . $e->getMessage());
}
try {
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$dbh->beginTransaction();
$stmt = $dbh->prepare('insert into CLOUD (name,date) VALUES(:customerName,:firstDay)');
$stmt->execute([
'customerName' => $_POST['customerName'],
'firstDay' => $_POST['firstDay']
]);
$cloud_id = $dbh->lastInsertId();
$stmt = $dbh->prepare('insert into IDC (name,id,phone,cloudid) VALUES(:name,:id,:phone,:cloudid)');
$stmt->bindParam(':name', $name);
$stmt->bindParam(':id', $id);
$stmt->bindParam(':phone', $phone);
$stmt->bindParam(':cloudid', $cloud_id);
$name = $_POST['engName3'];
$id = $_POST['engID3'];
$phone = $_POST['engPhone3'];
$stmt->execute();
$name = $_POST['engName4'];
$id = $_POST['engID4'];
$phone = $_POST['engPhone4'];
$stmt->execute();
$dbh->commit();
} catch (PDOException $e) {
$dbh->rollBack();
echo "Failed: " . $e->getMessage();
}
}