rollback if one of multple inserts fails using prepared statements - php

Question

I have a form script that inserts data in multiple tables. But if one fails it has to revert everything back. I've been looking for this but I didn't find a question that uses multiple (mysqli) prepared statements and rollback.
$mysqli = new mysqli(/* connection details */);
$mysqli->autocommit(FALSE);
// rollback should revert here
$mysqli->begin_transaction();
if ($stmt_one = $mysqli->prepare('INSERT INTO main_table (one, two, three) VALUES (?, ?, ?)')) {
$stmt_one->bind_param('sss', $one, $two, $three);
$stmt_one->execute();
$id = (int) $mysqli->insert_id;
if ($stmt_two = $mysqli->prepare('INSERT INTO sub_table_one (id, four) VALUES (?, ?)')) {
$stmt_two->bind_param('is', $id, $four);
$stmt_two->execute();
}
if ($stmt_three = $mysqli->prepare('INSERT INTO sub_table_two (id, five) VALUES (?, ?)')) {
$stmt_three->bind_param('is', $id, $five);
$stmt_three->execute();
}
}
if ($mysqli->commit()) {
// everything ok
header('Location: /');
} else {
// something went wrong, we have to rollback
$mysqli->rollback();
// and display the error message
echo $stmt_one->error;
echo $stmt_two->error;
echo $stmt_three->error;
}
I'm not sure about this, can I do something like that? Or do I have to check every $stmt_* for errors?
UPDATE
(The problem was that I was using DB Engine MyISAM instead of InnoDB)
I've upgraded to PHP 7 and now rollback is not working. I've tried the following:
if (!$mysqli->rollback()) $log .= 'no rollback :(';
But I don't see that message in my log...
My current code looks like:
public function Upload() {
try {
// rollback should revert here
$mysqli->begin_transaction();
// multiple prepared statements
if ($mysqli->commit()) {
$exit = $log;
} else {
throw new Exception('Transaction commit failed. Property ID: ' . $this->id);
}
} catch (Exception $e) {
try {
$test = $this->owner['id'] ? 'property' : ($this->applicant ? 'demand' : 'Fatal Error: PropertyFromInput() contact error (no owner, no applicant)');
$log = 'Rolling back new ' . $test . ' upload' . "\n";
if (!$mysqli->rollback()) $log .= 'no rollback...' . "\n";
if ($test == 'property') $log .= $this->cleanup_prop() ? 'property successfully cleaned up' . "\n" : 'error while cleaning up property' . "\n";
$err_msg = $e->getMessage();
} catch (Exception $f) {
$err_msg .= $f->getMessage();
}
$usr_msg = $upload_err ? $err_msg : 'Se ha producido un error. Por favor contacte con un administrador.';
$log .= 'User triggered an error while uploading a new ' . $test . ".\n" . 'Error message: ' . $err_msg;
$exit = array($log, $usr_msg);
}
$mysqli->autocommit(TRUE);
return $exit;
}
My log looks like:
Logging new property upload...
Rolling back new property upload
property successfully cleaned up
User triggered an error while uploading a new property.
Error message: Upload Error: $thumbnailsPath is false and/or not a dir: ". Property ID: 200
That means rollback() was executed/ didn't return false but the tables were inserted anyways...
Now about the new php features since 5.4:
5.5 added the finally block, do I just use it for setting autocommit to true?
I read php 7 improved the errors handling but I really have no idea how to take advantage of this.
I need this fixed because I wouldn't like my production db ending full of broken/unused data, who would?

Answer 1

As Xorifelse mentioned, your best option is to use try and catch even if you can't use finally. I've never used mysqli but I am assuming it is similar to PDO where you would do something like this:
$redirect = false;
try {
$mysqli = new mysqli(...);
$mysqli->autocommit(FALSE);
// rollback should revert here
$mysqli->begin_transaction();
if ($stmt_one = $mysqli->prepare('INSERT INTO main_table (one, two, three) VALUES (?, ?, ?)')) {
$stmt_one->bind_param('sss', $one, $two, $three);
if (!$stmt_one->execute()) {
throw new Exception($stmt_one->error);
}
$id = (int) $mysqli->insert_id;
if ($stmt_two = $mysqli->prepare('INSERT INTO sub_table_one (id, four) VALUES (?, ?)')) {
$stmt_two->bind_param('is', $id, $four);
if (!$stmt_two->execute()) {
throw new Exception($stmt_two->error);
}
}
if ($stmt_three = $mysqli->prepare('INSERT INTO sub_table_two (id, five) VALUES (?, ?)')) {
$stmt_three->bind_param('is', $id, $five);
if (!$stmt_three->execute()) {
throw new Exception($stmt_three->error);
}
}
}
if ($mysqli->commit()) {
$redirect = true;
} else {
throw new Exception('Transaction commit failed.');
}
} catch (Exception $e) {
try {
// something went wrong, we have to rollback
$mysqli->rollback();
// and display the error message
echo $e->getMessage();
} catch (Exception $f) {
// and display the error message
echo $f->getMessage();
}
}
// don't forget to do this also
$mysqli->autocommit(TRUE);
if ($redirect) {
header('Location: /');
}
In regards to the last line,
According to http://www.php.net/manual/en/mysqli.commit.php#89976,
calling $mysqli->commit() will NOT automatically set autocommit() back
to 'true'. That means that any queries following $mysqli->commit() will
be rolled back when your script exits, if autocommit() will be not
switched back to TRUE.