Syntax error when running multiple queries through mysqli - php

Question

I‘m trying to move rows from one table to another, when they‘re older than 6 hours. While my code works perfectly in PMA, I just get an error via PHP.
This is my PHP code:
$conn = mysqli_connect($servername, $username, $password, $dbname);
if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
$timestamp6h = time() - 21600;
$sql="BEGIN;
INSERT INTO archiv6h SELECT * FROM links WHERE tweettimestamp < $timestamp6h
ON DUPLICATE KEY UPDATE archiv6h.tweetscount= archiv6h.tweetscount+ links.tweetscount, archiv6h.followerscount= archiv6h.followerscount + links.followerscount, archiv6h.tweettimestamp= archiv6h.tweettimestamp + links.tweettimestamp;
DELETE FROM links WHERE tweettimestamp < $timestamp6h;
COMMIT;";
if (!mysqli_query($conn, $sql)) {
printf("Errormessage: %s\n", mysqli_error($conn));
}
$result = mysqli_query($conn, $sql);
$conn->close();
I then get the following error message:
Errormessage:
You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'INSERT INTO archiv6h SELECT * FROM links WHERE tweettimestamp < 1521038638 ON ' at line 1
When I use this as a query in PMA, it works like intended:
BEGIN;
INSERT INTO archiv6h SELECT * FROM `links` WHERE tweettimestamp < 1521038638
ON DUPLICATE KEY UPDATE archiv6h.tweetscount= archiv6h.tweetscount+ links.tweetscount, archiv6h.followerscount= archiv6h.followerscount + links.followerscount, archiv6h.tweettimestamp= archiv6h.tweettimestamp + links.tweettimestamp;
DELETE FROM `links` WHERE tweettimestamp < 1521038638;
COMMIT;
Has someone an idea how to get the query running in PHP?

Answer 1

With BEGIN; and COMMIT; that are four statements. You can't run multiple statements in one mysqli_query() call. If you need a transaction, use mysqli::begin_transaction(). And only use one statement per mysqli_query() call:
$conn->begin_transaction();
$conn->query("INSERT ...");
$conn->query("DELETE ...");
$conn->commit();
Note that you should also configure mysqli to throw exceptions. I would write your script the following way:
// set connection variables
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$conn = mysqli_connect($servername, $username, $password, $dbname);
$timestamp6h = time() - 21600;
$conn->begin_transaction();
$conn->query("
INSERT INTO archiv6h SELECT * FROM links WHERE tweettimestamp < $timestamp6h
ON DUPLICATE KEY UPDATE
archiv6h.tweetscount = archiv6h.tweetscount + links.tweetscount,
archiv6h.followerscount = archiv6h.followerscount + links.followerscount,
archiv6h.tweettimestamp = archiv6h.tweettimestamp + links.tweettimestamp
");
$conn->query("DELETE FROM links WHERE tweettimestamp < $timestamp6h");
$conn->commit();
If anything fails, $conn->commit(); will never be executed, and the script will output an error message. Threre is not even a need to close the conection, since it will be closed when the script ends.