Cannot create new account with PHP script

I’m struggling with the following webpage which belongs to a Gameserver to create a new account within the SQL Database. Now the problem is, for some reason, as soon as I click the register button, nothing happens. With the Developer tool I’ve found out an error message will be thrown as soon as Register has been clicked.
This is the error message :
Fatal error: uncaught Error. Non static method Database::getData() cannot be called statically in (…. pathname)

Kind regards,

Chris

I Already tried some sollutions mentioned on the internet.
For example to replace the Database::getData() to $Databse->getData() but this does not seem to work, or i’m doing something wrong.

This is my register.php file:

<?php
require 'vendor/autoload.php';
include_once('config/database.php');
include_once('config/config.php');
include_once('config/helper.php');

$config = new Config();
$request_params = getRequests();

$submitted_username = '';
$alert_message = '';
$relative_path = '';

if (!empty($_POST)) {
    $username = $_POST['username'];
    // Get user by username
    $db_user = $config->db_user;
    $sql = "SELECT * FROM dbo.TblAccount WHERE accountid = '$username'";
    $user_data  =  Database::getData($db_user, $sql, 'row');
    //$user_data = $dbName->getData($db_user, $sql, 'row');  <--- this I've tested.
    // Check password
    if ($user_data) {
        echo 0;
        die;
    }else{
        $hash_password = md5($_POST['password']);
        $db_user = $config->db_user;
        $sql = "EXEC dbo.regnewaccount '$username','$hash_password'";
        $user_data  = Database::getData($db_user, $sql, 'row');
        echo 1;
        die;
    }
}
?>

(Edit: This is the current Database.php script)

<?php
error_reporting(E_ERROR | E_PARSE);

        
class Database
{
        private static $cont  = 'null';
    
    public function __construct() {
        exit('Init function is not allowed');
    }

    public static  function connect($db_data) {
        $dbName = $db_data['database'];
        $dbHost = $db_data['hostname'];
        $dbUsername = $db_data['username'];
        $dbUserPassword = $db_data['password'];
        $dbDriver = $db_data['dbdriver'];

        // One connection through whole application
        if ( null == self::$cont ) {
            try {
                switch($dbDriver){
                    case 'sqlsrv':
                        self::$cont = new PDO( "sqlsrv:server=".$dbHost."; Database=".$dbName.";", $dbUsername, $dbUserPassword);  
                        $conn->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );  
                        break;
                    default:
                        self::$cont =  new PDO( "mysql:host=".$dbHost.";"."dbname=".$dbName. ";charset=utf8", $dbUsername, $dbUserPassword);
                        break;
                }
            } catch(PDOException $e) {
                die($e->getMessage());
            }
        }

        return self::$cont;
    }

    public static function disconnect() {
        self::$cont = null;
    }

    public static function getData($db_data, $sql,$type="list"){
        self::connect($db_data);
        switch($type){
            case 'row':
                $raw_data = self::$cont->query($sql)->fetch(PDO::FETCH_ASSOC);
                break;
            default:
                $raw_data = self::$cont->query($sql)->fetchAll(PDO::FETCH_ASSOC);
                break;
        }
        self::disconnect();
        return $raw_data;
    }

    public function updateData($db_data, $sql){
        self::connect($db_data);
        $raw_data = self::$cont->exec($sql);
        self::disconnect();
        return $raw_data;
    }
}

?>

This is the Config.php file, which contains the credentials for the SQL connections.

<?php
class Config
{
    const ITEMS_PER_PAGE = '20';
    const RELATIVE_URL = '';

    public $db_data;
    public $db_mulegend_jp;

    public function __construct() {
        $db_data['dbdriver'] = 'sqlsrv';
        $db_data['hostname'] = '192.168.XXX.XXX';
        $db_data['username'] = 'USER';
        $db_data['password'] = 'TEST';
        $db_data['database'] = 'Mu2Auth';
        

        $db_mulegend_jp['hostname'] = 'localhost';
        $db_mulegend_jp['username'] = 'root';
        $db_mulegend_jp['password'] = 'TEST';
        $db_mulegend_jp['database'] = 'mulegend_jp';
        $db_mulegend_jp['dbdriver'] = 'mysqli';

        $this->db_user = $db_user;
        $this->db_mulegend_jp = $db_mulegend_jp;
      }

}