SLIM3 - Accessing Database container in own Class

Question

I am writing my own classes in my Slim 3 Application. I'd like to have an own class to process Database Queries. Code looks like this:

<?php
class DatabaseOperator { 

    private $dbconnection;
    function __construct($dbconnection) {
        $this->dbconnection = $dbconnection;
    }

    public function getUserPermissions($user_id) {
        $user_permissions = "SELECT list_id FROM permissions WHERE user_id='$user_id'";
        $sth = $dbconnection->prepare($user_permissions);
        $sth->execute();
        $user_permissions_result = $sth->fetchAll();
        $result_permissions = array();
        foreach ($user_permissions_result as $row) {
            $list_id = $row['list_id'];
            $this->logger->info("User has access to List ID: " . $list_id);
            array_push($result_permissions, $list_id);
        }
        return $result_permissions;
    }

    public function getUserID($username) {
        $sqluser = "SELECT user_id FROM users WHERE username='$username'";
        // TODO: Android REG_ID from DB
        $sth = $dbconnection->prepare($sqluser);
        $sth->execute();
        $res = $sth->fetch(PDO::FETCH_ASSOC);
        return $res['user_id'];
    }
}
?>

In my routes.php I got something like this:

$app->get('/login', function (Request $request, Response $response, array $args) {
  $username = $request->getServerParam('PHP_AUTH_USER');
    if (isset($username)) {
      $this->logger->info("Authenticated user: " . $username);
      $databaseOperator = new DatabaseOperator($this->db);
      $user_id = $databaseOperator->getUserID($username);

But accessing the route gives me this error:

The application could not run because of the following error:
Call to a member function prepare() on null
File: /var/www/vhosts/hosting114426.a2f69.netcup.net/httpdocs/rememberly/classes/DatabaseOperator.php Line: 25
Trace< #0 /var/www/vhosts/hosting114426.a2f69.netcup.net/httpdocs/rememberly/src/routes.php(209): DatabaseOperator->getUserID('testuser')

So there seems to be an issue with the $dbconnection being null. But if I use $this->db->prepare(QUERY) in my routes.php it works without problems. So $this->db is not null.

So what is the problem here?

Answer 1

<?php
$slimSettings = [
/* ... */
];
$container = new \Slim\Container(['settings' => $slimSettings]);
$container['db'] = function ($c) {
    $dns = ''; // PDO dns
    $dbUser = ''; // database user
    $dbPass = ''; // database password
    return new \PDO($dns, $dbUser, $dbPass);
};

/* ... */
$app = new \Slim\App($container);
/* ... */
$app->get('/login', function (Request $request, Response $response, array $args) {
    $username = $request->getServerParam('PHP_AUTH_USER');
    if (isset($username)) {
        $this->logger->info("Authenticated user: " . $username);
        $databaseOperator = new DatabaseOperator($this->db);
        $user_id = $databaseOperator->getUserID($username);
    }
});