找不到PHP PDO驱动程序

Question

I have issues with my PHP installation under Ubuntu 16.04 LTS. I am getting the error: the driver is not found 1. I already tried the fix from the following post: PDOException “could not find driver” but it doesn't work. I am running Apache2 with a PHP7.2 Installation. If I run phpinfo() I can see, that it's
"PHP Version 7.2.7-1+ubuntu16.04.1+deb.sury.org+1"
and I can see the PDO extension and the pdo_mysql extension, so theoretically it should find the driver. Both states enabled.

The Script im calling:

<?php
include("sqlconnection.php");
$statement = $pdo->prepare("SELECT * FROM reaktor WHERE reactorID = 1");
$result = $statement->execute();
$return = $statement->fetchAll();
echo json_encode($return);
?>

The sqlconnection.php:

<?php
  $serverName = "nw-system.de";
  $dbName = "openComputers";
  $username = "";
  $passwort = "";
  try{
    $pdo = new PDO("sqlsrv:server=$serverName ; Database=$dbName", $username, $passwort);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  }
  catch(Exception $e)
  {
    exit(print_r($e->getMessage()));
  }
?>

I have deleted the username and password on purpouse

Any Ideas on how to fix this?
Kind regards
Jan