Maria DB updates multiple values ​​not working

Question

I have a project in which I create a plugin for Wordpress that will allow users to add, delete or update values ​​in the Maria database database.

My syntax is as follows:

try {
    $db = new PDO('mysql:host=HOST.mysql;dbname=DBNAME;charset=utf8', 'USERNAME',    'PASSWORD');
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
}
catch (PDOException $e)
{
    echo $e->getMessage();
}

This will initialize the contact with the database. If the administrator clicks on the "edit" button, this code will be called.

$updatequery = "UPDATE property SET Seller = '$Seller',
Agent = '$Agent',
Country = '$Country',
City = '$City',
Status = '$Status',
Rentprice = '$Rentprice',
Sellprice = '$Sellprice',
Kitchen = '$Kitchen',
Bedrooms = '$Bedrooms',
Bathrooms = '$Bathrooms',
Rooms = '$Rooms',
Post = '$Post',
Description = '$Description',
Beskrivning = '$Beskrivning',
Caption = '$Caption',
IMG = '$IMG' WHERE ID ='$ID';";

$STH = $db->query($updatequery);

echo "<script>alert('The property has been updated, have a nice day !')</script>";

When I click the edit button. A warning message is displayed, which means that the code has been called. But the values ​​have not been changed. However, despite this, there is no error message, as it was before, when I had fixes for syntax errors that I fixed.

Does the fact that the database runs on MariaDB instead of Mysql mean which syntax will be adopted? Or am I missing something?

MariaDB - 5.5.39-MariaDB.

.