PHP MYSQL错误1064 [关闭]

I can't tell what is wrong with this because I've used similar queries the same way and there isn't an issue. It is giving me the following error:

Multi query failed: (1064) 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 'UPDATE stock SET quantity='160' WHERE id='2'' at line 1

If someone could take a look and see if i'm missing something:

$root = $_SERVER['DOCUMENT_ROOT']."/wfo-inv";

require ($root.'/assets/config.php');

$id = $_GET['id'];

$link = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_DATABASE);

// Check connection
if($link === false){
    die("ERROR: Could not connect. " . mysqli_connect_error());
}

// Escape user inputs for security
$name = mysqli_real_escape_string($link, $_POST['name']);
$type = mysqli_real_escape_string($link, $_POST['type']);
$quantity = mysqli_real_escape_string($link, $_POST['quantity']);
$quantitysold = mysqli_real_escape_string($link, $_POST['quantitysold']);
$price = mysqli_real_escape_string($link, $_POST['price']);
$location = mysqli_real_escape_string($link, $_POST['location']);
$batch = mysqli_real_escape_string($link, $_POST['batch']);
$thc = mysqli_real_escape_string($link, $_POST['thc']);
$cbd = mysqli_real_escape_string($link, $_POST['cbd']);

$quantityfinal = $quantity - $quantitysold;

if($quantityfinal >= "1") {
        $sql = "INSERT INTO outgoing (name, type, quantity, price, location, batch, thc, cbd) VALUES ('$name', '$type', '$quantitysold', '$price', '$location', '$batch', '$thc', '$cbd')";
        $sql .= "UPDATE stock SET quantity='$quantityfinal' WHERE id='$id'";
} else {
        $sql = "INSERT INTO outgoing (name, type, quantity, price, location, batch, thc, cbd) VALUES ('$name', '$type', '$quantitysold', '$price', '$location', '$batch', '$thc', '$cbd')";
        $sql .= "DELETE FROM stock WHERE id='$id'";
}

if (!$link->multi_query($sql)) {
    echo "Multi query failed: (" . $link->errno . ") " . $link->error;
}

do {
    if ($res = $link->store_result()) {
        var_dump($res->fetch_all(MYSQLI_ASSOC));
        $res->free();
        header("Location: ../index.php");
    }
} while ($link->more_results() && $link->next_result());



// close connection
mysqli_close($link);

According to the docs, the queries passed to mysqli::multiquery() need to be concatenated with a semicolon, something like

$sql = "INSERT INTO outgoing (name, type, quantity, price, location, batch, thc, cbd) VALUES ('$name', '$type', '$quantitysold', '$price', '$location', '$batch', '$thc', '$cbd')";
$sql .= "; "; // <- Add this line here
$sql .= "UPDATE stock SET quantity='$quantityfinal' WHERE id='$id'";

(It doesn't have to be on a separate line, of course; I just did that to make it obvious.)

Take the apostrophes from around the two variables in that line and replace them with open and close curly braces, that should fix the line.

"update table set column={$var} where column={$othervar}"